<!-- doc/src/sgml/catalogs.sgml -->
<!--
 Documentation of the system catalogs, directed toward PostgreSQL developers
 -->

<chapter id="catalogs">
 <title>System Catalogs</title>

  <para>
   The system catalogs are the place where a relational database
   management system stores schema metadata, such as information about
   tables and columns, and internal bookkeeping information.
   <productname>PostgreSQL</productname>'s system catalogs are regular
   tables.  You can drop and recreate the tables, add columns, insert
   and update values, and severely mess up your system that way.
   Normally, one should not change the system catalogs by hand, there
   are normally SQL commands to do that.  (For example, <command>CREATE
   DATABASE</command> inserts a row into the
   <structname>pg_database</structname> catalog &mdash; and actually
   creates the database on disk.)  There are some exceptions for
   particularly esoteric operations, but many of those have been made
   available as SQL commands over time, and so the need for direct manipulation
   of the system catalogs is ever decreasing.
  </para>

 <sect1 id="catalogs-overview">
  <title>Overview</title>

  <para>
   <xref linkend="catalog-table"/> lists the system catalogs.
   More detailed documentation of each catalog follows below.
  </para>

  <para>
   Most system catalogs are copied from the template database during
   database creation and are thereafter database-specific. A few
   catalogs are physically shared across all databases in a cluster;
   these are noted in the descriptions of the individual catalogs.
  </para>

  <table id="catalog-table">
   <title>System Catalogs</title>

   <tgroup cols="2">
    <thead>
     <row>
      <entry>Catalog Name</entry>
      <entry>Purpose</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><link linkend="catalog-pg-aggregate"><structname>pg_aggregate</structname></link></entry>
      <entry>aggregate functions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-am"><structname>pg_am</structname></link></entry>
      <entry>relation access methods</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-amop"><structname>pg_amop</structname></link></entry>
      <entry>access method operators</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-amproc"><structname>pg_amproc</structname></link></entry>
      <entry>access method support functions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-attrdef"><structname>pg_attrdef</structname></link></entry>
      <entry>column default values</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link></entry>
      <entry>table columns (<quote>attributes</quote>)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link></entry>
      <entry>authorization identifiers (roles)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-auth-members"><structname>pg_auth_members</structname></link></entry>
      <entry>authorization identifier membership relationships</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-cast"><structname>pg_cast</structname></link></entry>
      <entry>casts (data type conversions)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-class"><structname>pg_class</structname></link></entry>
      <entry>tables, indexes, sequences, views (<quote>relations</quote>)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-collation"><structname>pg_collation</structname></link></entry>
      <entry>collations (locale information)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link></entry>
      <entry>check constraints, unique constraints, primary key constraints, foreign key constraints</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-conversion"><structname>pg_conversion</structname></link></entry>
      <entry>encoding conversion information</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-database"><structname>pg_database</structname></link></entry>
      <entry>databases within this database cluster</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-db-role-setting"><structname>pg_db_role_setting</structname></link></entry>
      <entry>per-role and per-database settings</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-default-acl"><structname>pg_default_acl</structname></link></entry>
      <entry>default privileges for object types</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-depend"><structname>pg_depend</structname></link></entry>
      <entry>dependencies between database objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-description"><structname>pg_description</structname></link></entry>
      <entry>descriptions or comments on database objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-enum"><structname>pg_enum</structname></link></entry>
      <entry>enum label and value definitions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-event-trigger"><structname>pg_event_trigger</structname></link></entry>
      <entry>event triggers</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-extension"><structname>pg_extension</structname></link></entry>
      <entry>installed extensions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-foreign-data-wrapper"><structname>pg_foreign_data_wrapper</structname></link></entry>
      <entry>foreign-data wrapper definitions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link></entry>
      <entry>foreign server definitions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-foreign-table"><structname>pg_foreign_table</structname></link></entry>
      <entry>additional foreign table information</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-index"><structname>pg_index</structname></link></entry>
      <entry>additional index information</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-inherits"><structname>pg_inherits</structname></link></entry>
      <entry>table inheritance hierarchy</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-init-privs"><structname>pg_init_privs</structname></link></entry>
      <entry>object initial privileges</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-language"><structname>pg_language</structname></link></entry>
      <entry>languages for writing functions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-largeobject"><structname>pg_largeobject</structname></link></entry>
      <entry>data pages for large objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-largeobject-metadata"><structname>pg_largeobject_metadata</structname></link></entry>
      <entry>metadata for large objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link></entry>
      <entry>schemas</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link></entry>
      <entry>access method operator classes</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-operator"><structname>pg_operator</structname></link></entry>
      <entry>operators</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link></entry>
      <entry>access method operator families</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-parameter-acl"><structname>pg_parameter_acl</structname></link></entry>
      <entry>configuration parameters for which privileges have been granted</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-partitioned-table"><structname>pg_partitioned_table</structname></link></entry>
      <entry>information about partition key of tables</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-policy"><structname>pg_policy</structname></link></entry>
      <entry>row-security policies</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link></entry>
      <entry>functions and procedures</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-publication"><structname>pg_publication</structname></link></entry>
      <entry>publications for logical replication</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-publication-namespace"><structname>pg_publication_namespace</structname></link></entry>
      <entry>schema to publication mapping</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-publication-rel"><structname>pg_publication_rel</structname></link></entry>
      <entry>relation to publication mapping</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-range"><structname>pg_range</structname></link></entry>
      <entry>information about range types</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-replication-origin"><structname>pg_replication_origin</structname></link></entry>
      <entry>registered replication origins</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-rewrite"><structname>pg_rewrite</structname></link></entry>
      <entry>query rewrite rules</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-seclabel"><structname>pg_seclabel</structname></link></entry>
      <entry>security labels on database objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-sequence"><structname>pg_sequence</structname></link></entry>
      <entry>information about sequences</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-shdepend"><structname>pg_shdepend</structname></link></entry>
      <entry>dependencies on shared objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-shdescription"><structname>pg_shdescription</structname></link></entry>
      <entry>comments on shared objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-shseclabel"><structname>pg_shseclabel</structname></link></entry>
      <entry>security labels on shared database objects</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-statistic"><structname>pg_statistic</structname></link></entry>
      <entry>planner statistics</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-statistic-ext"><structname>pg_statistic_ext</structname></link></entry>
      <entry>extended planner statistics (definition)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-statistic-ext-data"><structname>pg_statistic_ext_data</structname></link></entry>
      <entry>extended planner statistics (built statistics)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-subscription"><structname>pg_subscription</structname></link></entry>
      <entry>logical replication subscriptions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-subscription-rel"><structname>pg_subscription_rel</structname></link></entry>
      <entry>relation state for subscriptions</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link></entry>
      <entry>tablespaces within this database cluster</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-transform"><structname>pg_transform</structname></link></entry>
      <entry>transforms (data type to procedural language conversions)</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link></entry>
      <entry>triggers</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-ts-config"><structname>pg_ts_config</structname></link></entry>
      <entry>text search configurations</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-ts-config-map"><structname>pg_ts_config_map</structname></link></entry>
      <entry>text search configurations' token mappings</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-ts-dict"><structname>pg_ts_dict</structname></link></entry>
      <entry>text search dictionaries</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-ts-parser"><structname>pg_ts_parser</structname></link></entry>
      <entry>text search parsers</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-ts-template"><structname>pg_ts_template</structname></link></entry>
      <entry>text search templates</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-type"><structname>pg_type</structname></link></entry>
      <entry>data types</entry>
     </row>

     <row>
      <entry><link linkend="catalog-pg-user-mapping"><structname>pg_user_mapping</structname></link></entry>
      <entry>mappings of users to foreign servers</entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-aggregate">
  <title><structname>pg_aggregate</structname></title>

  <indexterm zone="catalog-pg-aggregate">
   <primary>pg_aggregate</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_aggregate</structname> stores information about
   aggregate functions.  An aggregate function is a function that
   operates on a set of values (typically one column from each row
   that matches a query condition) and returns a single value computed
   from all these values.  Typical aggregate functions are
   <function>sum</function>, <function>count</function>, and
   <function>max</function>.  Each entry in
   <structname>pg_aggregate</structname> is an extension of an entry
   in <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.
   The <structname>pg_proc</structname> entry carries the aggregate's name,
   input and output data types, and other information that is similar to
   ordinary functions.
  </para>

  <table>
   <title><structname>pg_aggregate</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggfnoid</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       <structname>pg_proc</structname> OID of the aggregate function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggkind</structfield> <type>char</type>
      </para>
      <para>
       Aggregate kind:
       <literal>n</literal> for <quote>normal</quote> aggregates,
       <literal>o</literal> for <quote>ordered-set</quote> aggregates, or
       <literal>h</literal> for <quote>hypothetical-set</quote> aggregates
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggnumdirectargs</structfield> <type>int2</type>
      </para>
      <para>
       Number of direct (non-aggregated) arguments of an ordered-set or
       hypothetical-set aggregate, counting a variadic array as one argument.
       If equal to <structfield>pronargs</structfield>, the aggregate must be variadic
       and the variadic array describes the aggregated arguments as well as
       the final direct arguments.
       Always zero for normal aggregates.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggtransfn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Transition function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggfinalfn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Final function (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggcombinefn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Combine function (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggserialfn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Serialization function (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggdeserialfn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Deserialization function (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggmtransfn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Forward transition function for moving-aggregate mode (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggminvtransfn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Inverse transition function for moving-aggregate mode (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggmfinalfn</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Final function for moving-aggregate mode (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggfinalextra</structfield> <type>bool</type>
      </para>
      <para>
       True to pass extra dummy arguments to <structfield>aggfinalfn</structfield>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggmfinalextra</structfield> <type>bool</type>
      </para>
      <para>
       True to pass extra dummy arguments to <structfield>aggmfinalfn</structfield>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggfinalmodify</structfield> <type>char</type>
      </para>
      <para>
       Whether <structfield>aggfinalfn</structfield> modifies the
       transition state value:
       <literal>r</literal> if it is read-only,
       <literal>s</literal> if the <structfield>aggtransfn</structfield>
       cannot be applied after the <structfield>aggfinalfn</structfield>, or
       <literal>w</literal> if it writes on the value
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggmfinalmodify</structfield> <type>char</type>
      </para>
      <para>
       Like <structfield>aggfinalmodify</structfield>, but for
       the <structfield>aggmfinalfn</structfield>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggsortop</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Associated sort operator (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggtranstype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Data type of the aggregate function's internal transition (state) data
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggtransspace</structfield> <type>int4</type>
      </para>
      <para>
       Approximate average size (in bytes) of the transition state
       data, or zero to use a default estimate
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggmtranstype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Data type of the aggregate function's internal transition (state)
       data for moving-aggregate mode (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggmtransspace</structfield> <type>int4</type>
      </para>
      <para>
       Approximate average size (in bytes) of the transition state data
       for moving-aggregate mode, or zero to use a default estimate
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>agginitval</structfield> <type>text</type>
      </para>
      <para>
       The initial value of the transition state.  This is a text
       field containing the initial value in its external string
       representation.  If this field is null, the transition state
       value starts out null.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>aggminitval</structfield> <type>text</type>
      </para>
      <para>
       The initial value of the transition state for moving-aggregate mode.
       This is a text field containing the initial value in its external
       string representation.  If this field is null, the transition state
       value starts out null.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   New aggregate functions are registered with the <link
   linkend="sql-createaggregate"><command>CREATE AGGREGATE</command></link>
   command.  See <xref linkend="xaggr"/> for more information about
   writing aggregate functions and the meaning of the transition
   functions, etc.
  </para>

 </sect1>


 <sect1 id="catalog-pg-am">
  <title><structname>pg_am</structname></title>

  <indexterm zone="catalog-pg-am">
   <primary>pg_am</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_am</structname> stores information about
   relation access methods.  There is one row for each access method supported
   by the system.
   Currently, only tables and indexes have access methods. The requirements for table
   and index access methods are discussed in detail in <xref linkend="tableam"/> and
   <xref linkend="indexam"/> respectively.
  </para>

  <table>
   <title><structname>pg_am</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amname</structfield> <type>name</type>
      </para>
      <para>
       Name of the access method
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amhandler</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of a handler function that is responsible for supplying information
       about the access method
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amtype</structfield> <type>char</type>
      </para>
      <para>
       <literal>t</literal> = table (including materialized views),
       <literal>i</literal> = index.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <note>
   <para>
    Before <productname>PostgreSQL</productname> 9.6, <structname>pg_am</structname>
    contained many additional columns representing properties of index access
    methods.  That data is now only directly visible at the C code level.
    However, <function>pg_index_column_has_property()</function> and related
    functions have been added to allow SQL queries to inspect index access
    method properties; see <xref linkend="functions-info-catalog-table"/>.
   </para>
  </note>

 </sect1>


 <sect1 id="catalog-pg-amop">
  <title><structname>pg_amop</structname></title>

  <indexterm zone="catalog-pg-amop">
   <primary>pg_amop</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_amop</structname> stores information about
   operators associated with access method operator families.  There is one
   row for each operator that is a member of an operator family.  A family
   member can be either a <firstterm>search</firstterm> operator or an
   <firstterm>ordering</firstterm> operator.  An operator
   can appear in more than one family, but cannot appear in more than one
   search position nor more than one ordering position within a family.
   (It is allowed, though unlikely, for an operator to be used for both
   search and ordering purposes.)
  </para>

  <table>
   <title><structname>pg_amop</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amopfamily</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The operator family this entry is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amoplefttype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Left-hand input data type of operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amoprighttype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Right-hand input data type of operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amopstrategy</structfield> <type>int2</type>
      </para>
      <para>
       Operator strategy number
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amoppurpose</structfield> <type>char</type>
      </para>
      <para>
       Operator purpose, either <literal>s</literal> for search or
       <literal>o</literal> for ordering
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amopopr</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amopmethod</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-am"><structname>pg_am</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Index access method operator family is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amopsortfamily</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The B-tree operator family this entry sorts according to, if an
       ordering operator; zero if a search operator
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   A <quote>search</quote> operator entry indicates that an index of this operator
   family can be searched to find all rows satisfying
   <literal>WHERE</literal>
   <replaceable>indexed_column</replaceable>
   <replaceable>operator</replaceable>
   <replaceable>constant</replaceable>.
   Obviously, such an operator must return <type>boolean</type>, and its left-hand input
   type must match the index's column data type.
  </para>

  <para>
   An <quote>ordering</quote> operator entry indicates that an index of this
   operator family can be scanned to return rows in the order represented by
   <literal>ORDER BY</literal>
   <replaceable>indexed_column</replaceable>
   <replaceable>operator</replaceable>
   <replaceable>constant</replaceable>.
   Such an operator could return any sortable data type, though again
   its left-hand input type must match the index's column data type.
   The exact semantics of the <literal>ORDER BY</literal> are specified by the
   <structfield>amopsortfamily</structfield> column, which must reference
   a B-tree operator family for the operator's result type.
  </para>

  <note>
   <para>
    At present, it's assumed that the sort order for an ordering operator
    is the default for the referenced operator family, i.e., <literal>ASC NULLS
    LAST</literal>.  This might someday be relaxed by adding additional columns
    to specify sort options explicitly.
   </para>
  </note>

  <para>
   An entry's <structfield>amopmethod</structfield> must match the
   <structfield>opfmethod</structfield> of its containing operator family (including
   <structfield>amopmethod</structfield> here is an intentional denormalization of the
   catalog structure for performance reasons).  Also,
   <structfield>amoplefttype</structfield> and <structfield>amoprighttype</structfield> must match
   the <structfield>oprleft</structfield> and <structfield>oprright</structfield> fields of the
   referenced <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link> entry.
  </para>

 </sect1>


 <sect1 id="catalog-pg-amproc">
  <title><structname>pg_amproc</structname></title>

  <indexterm zone="catalog-pg-amproc">
   <primary>pg_amproc</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_amproc</structname> stores information about
   support functions associated with access method operator families.  There
   is one row for each support function belonging to an operator family.
  </para>

  <table>
   <title><structname>pg_amproc</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amprocfamily</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The operator family this entry is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amproclefttype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Left-hand input data type of associated operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amprocrighttype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Right-hand input data type of associated operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amprocnum</structfield> <type>int2</type>
      </para>
      <para>
       Support function number
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>amproc</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the function
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   The usual interpretation of the
   <structfield>amproclefttype</structfield> and <structfield>amprocrighttype</structfield> fields
   is that they identify the left and right input types of the operator(s)
   that a particular support function supports.  For some access methods
   these match the input data type(s) of the support function itself, for
   others not.  There is a notion of <quote>default</quote> support functions for
   an index, which are those with <structfield>amproclefttype</structfield> and
   <structfield>amprocrighttype</structfield> both equal to the index operator class's
   <structfield>opcintype</structfield>.
  </para>

 </sect1>


 <sect1 id="catalog-pg-attrdef">
  <title><structname>pg_attrdef</structname></title>

  <indexterm zone="catalog-pg-attrdef">
   <primary>pg_attrdef</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_attrdef</structname> stores column default
   values.  The main information about columns is stored in
   <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.
   Only columns for which a default value has been explicitly set will have
   an entry here.
  </para>

  <table>
   <title><structname>pg_attrdef</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>adrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table this column belongs to
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>adnum</structfield> <type>int2</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       The number of the column
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>adbin</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       The column default value, in <function>nodeToString()</function>
       representation.  Use <literal>pg_get_expr(adbin, adrelid)</literal> to
       convert it to an SQL expression.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-attribute">
  <title><structname>pg_attribute</structname></title>

  <indexterm zone="catalog-pg-attribute">
   <primary>pg_attribute</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_attribute</structname> stores information about
   table columns.  There will be exactly one
   <structname>pg_attribute</structname> row for every column in every
   table in the database.  (There will also be attribute entries for
   indexes, and indeed all objects that have
   <link linkend="catalog-pg-class"><structname>pg_class</structname></link>
   entries.)
  </para>

  <para>
   The term attribute is equivalent to column and is used for
   historical reasons.
  </para>

  <table>
   <title><structname>pg_attribute</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table this column belongs to
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attname</structfield> <type>name</type>
      </para>
      <para>
       The column name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>atttypid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The data type of this column (zero for a dropped column)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attstattarget</structfield> <type>int4</type>
      </para>
      <para>
       <structfield>attstattarget</structfield> controls the level of detail
       of statistics accumulated for this column by
       <link linkend="sql-analyze"><command>ANALYZE</command></link>.
       A zero value indicates that no statistics should be collected.
       A negative value says to use the system default statistics target.
       The exact meaning of positive values is data type-dependent.
       For scalar data types, <structfield>attstattarget</structfield>
       is both the target number of <quote>most common values</quote>
       to collect, and the target number of histogram bins to create.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attlen</structfield> <type>int2</type>
      </para>
      <para>
       A copy of <literal>pg_type.typlen</literal> of this column's
       type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attnum</structfield> <type>int2</type>
      </para>
      <para>
       The number of the column.  Ordinary columns are numbered from 1
       up.  System columns, such as <structfield>ctid</structfield>,
       have (arbitrary) negative numbers.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attndims</structfield> <type>int4</type>
      </para>
      <para>
       Number of dimensions, if the column is an array type; otherwise 0.
       (Presently, the number of dimensions of an array is not enforced,
       so any nonzero value effectively means <quote>it's an array</quote>.)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attcacheoff</structfield> <type>int4</type>
      </para>
      <para>
       Always -1 in storage, but when loaded into a row descriptor
       in memory this might be updated to cache the offset of the attribute
       within the row
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>atttypmod</structfield> <type>int4</type>
      </para>
      <para>
       <structfield>atttypmod</structfield> records type-specific data
       supplied at table creation time (for example, the maximum
       length of a <type>varchar</type> column).  It is passed to
       type-specific input functions and length coercion functions.
       The value will generally be -1 for types that do not need <structfield>atttypmod</structfield>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attbyval</structfield> <type>bool</type>
      </para>
      <para>
       A copy of <literal>pg_type.typbyval</literal> of this column's type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attalign</structfield> <type>char</type>
      </para>
      <para>
       A copy of <literal>pg_type.typalign</literal> of this column's type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attstorage</structfield> <type>char</type>
      </para>
      <para>
       Normally a copy of <literal>pg_type.typstorage</literal> of this
       column's type.  For TOAST-able data types, this can be altered
       after column creation to control storage policy.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attcompression</structfield> <type>char</type>
      </para>
      <para>
       The current compression method of the column.  Typically this is
       <literal>'\0'</literal> to specify use of the current default setting
       (see <xref linkend="guc-default-toast-compression"/>).  Otherwise,
       <literal>'p'</literal> selects pglz compression, while
       <literal>'l'</literal> selects <productname>LZ4</productname>
       compression.  However, this field is ignored
       whenever <structfield>attstorage</structfield> does not allow
       compression.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attnotnull</structfield> <type>bool</type>
      </para>
      <para>
       This represents a not-null constraint.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>atthasdef</structfield> <type>bool</type>
      </para>
      <para>
       This column has a default expression or generation expression, in which
       case there will be a corresponding entry in the
       <link linkend="catalog-pg-attrdef"><structname>pg_attrdef</structname></link> catalog that actually defines the
       expression.  (Check <structfield>attgenerated</structfield> to
       determine whether this is a default or a generation expression.)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>atthasmissing</structfield> <type>bool</type>
      </para>
      <para>
       This column has a value which is used where the column is entirely
       missing from the row, as happens when a column is added with a
       non-volatile <literal>DEFAULT</literal> value after the row is created.
       The actual value used is stored in the
       <structfield>attmissingval</structfield> column.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attidentity</structfield> <type>char</type>
      </para>
      <para>
       If a zero byte (<literal>''</literal>), then not an identity column.
       Otherwise, <literal>a</literal> = generated
       always, <literal>d</literal> = generated by default.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attgenerated</structfield> <type>char</type>
      </para>
      <para>
       If a zero byte (<literal>''</literal>), then not a generated column.
       Otherwise, <literal>s</literal> = stored.  (Other values might be added
       in the future.)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attisdropped</structfield> <type>bool</type>
      </para>
      <para>
       This column has been dropped and is no longer valid.  A dropped
       column is still physically present in the table, but is
       ignored by the parser and so cannot be accessed via SQL.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attislocal</structfield> <type>bool</type>
      </para>
      <para>
       This column is defined locally in the relation.  Note that a column can
       be locally defined and inherited simultaneously.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attinhcount</structfield> <type>int4</type>
      </para>
      <para>
       The number of direct ancestors this column has.  A column with a
       nonzero number of ancestors cannot be dropped nor renamed.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attcollation</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-collation"><structname>pg_collation</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The defined collation of the column, or zero if the column is
       not of a collatable data type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Column-level access privileges, if any have been granted specifically
       on this column
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attoptions</structfield> <type>text[]</type>
      </para>
      <para>
       Attribute-level options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attfdwoptions</structfield> <type>text[]</type>
      </para>
      <para>
       Attribute-level foreign data wrapper options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>attmissingval</structfield> <type>anyarray</type>
      </para>
      <para>
       This column has a one element array containing the value used when the
       column is entirely missing from the row, as happens when the column is
       added with a non-volatile <literal>DEFAULT</literal> value after the
       row is created.  The value is only used when
       <structfield>atthasmissing</structfield> is true.  If there is no value
       the column is null.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   In a dropped column's <structname>pg_attribute</structname> entry,
   <structfield>atttypid</structfield> is reset to zero, but
   <structfield>attlen</structfield> and the other fields copied from
   <link linkend="catalog-pg-type"><structname>pg_type</structname></link> are still valid.  This arrangement is needed
   to cope with the situation where the dropped column's data type was
   later dropped, and so there is no <structname>pg_type</structname> row anymore.
   <structfield>attlen</structfield> and the other fields can be used
   to interpret the contents of a row of the table.
  </para>
 </sect1>


 <sect1 id="catalog-pg-authid">
  <title><structname>pg_authid</structname></title>

  <indexterm zone="catalog-pg-authid">
   <primary>pg_authid</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_authid</structname> contains information about
   database authorization identifiers (roles).  A role subsumes the concepts
   of <quote>users</quote> and <quote>groups</quote>.  A user is essentially just a
   role with the <structfield>rolcanlogin</structfield> flag set.  Any role (with or
   without <structfield>rolcanlogin</structfield>) can have other roles as members; see
   <link linkend="catalog-pg-auth-members"><structname>pg_auth_members</structname></link>.
  </para>

  <para>
   Since this catalog contains passwords, it must not be publicly readable.
   <link linkend="view-pg-roles"><structname>pg_roles</structname></link>
   is a publicly readable view on
   <structname>pg_authid</structname> that blanks out the password field.
  </para>

  <para>
   <xref linkend="user-manag"/> contains detailed information about user and
   privilege management.
  </para>

  <para>
   Because user identities are cluster-wide,
   <structname>pg_authid</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_authid</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_authid</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolname</structfield> <type>name</type>
      </para>
      <para>
       Role name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolsuper</structfield> <type>bool</type>
      </para>
      <para>
       Role has superuser privileges
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolinherit</structfield> <type>bool</type>
      </para>
      <para>
       Role automatically inherits privileges of roles it is a
       member of
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolcreaterole</structfield> <type>bool</type>
      </para>
      <para>
       Role can create more roles
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolcreatedb</structfield> <type>bool</type>
      </para>
      <para>
       Role can create databases
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolcanlogin</structfield> <type>bool</type>
      </para>
      <para>
       Role can log in. That is, this role can be given as the initial
       session authorization identifier.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolreplication</structfield> <type>bool</type>
      </para>
      <para>
       Role is a replication role. A replication role can initiate replication
       connections and create and drop replication slots.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolbypassrls</structfield> <type>bool</type>
      </para>
      <para>
       Role bypasses every row-level security policy, see
       <xref linkend="ddl-rowsecurity"/> for more information.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolconnlimit</structfield> <type>int4</type>
      </para>
      <para>
       For roles that can log in, this sets maximum number of concurrent
       connections this role can make.  -1 means no limit.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolpassword</structfield> <type>text</type>
      </para>
      <para>
       Password (possibly encrypted); null if none. The format depends
       on the form of encryption used.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rolvaliduntil</structfield> <type>timestamptz</type>
      </para>
      <para>
       Password expiry time (only used for password authentication);
       null if no expiration
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   For an MD5 encrypted password, <structfield>rolpassword</structfield>
   column will begin with the string <literal>md5</literal> followed by a
   32-character hexadecimal MD5 hash. The MD5 hash will be of the user's
   password concatenated to their user name. For example, if user
   <literal>joe</literal> has password <literal>xyzzy</literal>, <productname>PostgreSQL</productname>
   will store the md5 hash of <literal>xyzzyjoe</literal>.
  </para>

  <para>
   If the password is encrypted with SCRAM-SHA-256, it has the format:
<synopsis>
SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&lt;salt&gt;</replaceable>$<replaceable>&lt;StoredKey&gt;</replaceable>:<replaceable>&lt;ServerKey&gt;</replaceable>
</synopsis>
   where <replaceable>salt</replaceable>, <replaceable>StoredKey</replaceable> and
   <replaceable>ServerKey</replaceable> are in Base64 encoded format. This format is
   the same as that specified by <ulink url="https://datatracker.ietf.org/doc/html/rfc5803">RFC 5803</ulink>.
  </para>

  <para>
    A password that does not follow either of those formats is assumed to be
    unencrypted.
  </para>
 </sect1>


 <sect1 id="catalog-pg-auth-members">
  <title><structname>pg_auth_members</structname></title>

  <indexterm zone="catalog-pg-auth-members">
   <primary>pg_auth_members</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_auth_members</structname> shows the membership
   relations between roles.  Any non-circular set of relationships is allowed.
  </para>

  <para>
   Because user identities are cluster-wide,
   <structname>pg_auth_members</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_auth_members</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_auth_members</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>roleid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       ID of a role that has a member
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>member</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       ID of a role that is a member of <structfield>roleid</structfield>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>grantor</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       ID of the role that granted this membership
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>admin_option</structfield> <type>bool</type>
      </para>
      <para>
       True if <structfield>member</structfield> can grant membership in
       <structfield>roleid</structfield> to others
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-cast">
  <title><structname>pg_cast</structname></title>

  <indexterm zone="catalog-pg-cast">
   <primary>pg_cast</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_cast</structname> stores data type conversion
   paths, both built-in and user-defined.
  </para>

  <para>
   It should be noted that <structname>pg_cast</structname> does not represent
   every type conversion that the system knows how to perform; only those that
   cannot be deduced from some generic rule.  For example, casting between a
   domain and its base type is not explicitly represented in
   <structname>pg_cast</structname>.  Another important exception is that
   <quote>automatic I/O conversion casts</quote>, those performed using a data
   type's own I/O functions to convert to or from <type>text</type> or other
   string types, are not explicitly represented in
   <structname>pg_cast</structname>.
  </para>

  <table>
   <title><structname>pg_cast</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>castsource</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the source data type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>casttarget</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the target data type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>castfunc</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the function to use to perform this cast.  Zero is
       stored if the cast method doesn't require a function.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>castcontext</structfield> <type>char</type>
      </para>
      <para>
       Indicates what contexts the cast can be invoked in.
       <literal>e</literal> means only as an explicit cast (using
       <literal>CAST</literal> or <literal>::</literal> syntax).
       <literal>a</literal> means implicitly in assignment
       to a target column, as well as explicitly.
       <literal>i</literal> means implicitly in expressions, as well as the
       other cases.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>castmethod</structfield> <type>char</type>
      </para>
      <para>
       Indicates how the cast is performed.
       <literal>f</literal> means that the function specified in the <structfield>castfunc</structfield> field is used.
       <literal>i</literal> means that the input/output functions are used.
       <literal>b</literal> means that the types are binary-coercible, thus no conversion is required.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   The cast functions listed in <structname>pg_cast</structname> must
   always take the cast source type as their first argument type, and
   return the cast destination type as their result type.  A cast
   function can have up to three arguments.  The second argument,
   if present, must be type <type>integer</type>; it receives the type
   modifier associated with the destination type, or -1
   if there is none.  The third argument,
   if present, must be type <type>boolean</type>; it receives <literal>true</literal>
   if the cast is an explicit cast, <literal>false</literal> otherwise.
  </para>

  <para>
   It is legitimate to create a <structname>pg_cast</structname> entry
   in which the source and target types are the same, if the associated
   function takes more than one argument.  Such entries represent
   <quote>length coercion functions</quote> that coerce values of the type
   to be legal for a particular type modifier value.
  </para>

  <para>
   When a <structname>pg_cast</structname> entry has different source and
   target types and a function that takes more than one argument, it
   represents converting from one type to another and applying a length
   coercion in a single step.  When no such entry is available, coercion
   to a type that uses a type modifier involves two steps, one to
   convert between data types and a second to apply the modifier.
  </para>
 </sect1>

 <sect1 id="catalog-pg-class">
  <title><structname>pg_class</structname></title>

  <indexterm zone="catalog-pg-class">
   <primary>pg_class</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_class</structname> describes tables and
   other objects that have columns or are otherwise similar to a
   table.  This includes indexes (but see also <link
   linkend="catalog-pg-index"><structname>pg_index</structname></link>),
   sequences (but see also <link
   linkend="catalog-pg-sequence"><structname>pg_sequence</structname></link>),
   views, materialized views, composite types, and TOAST tables;
   see <structfield>relkind</structfield>.
   Below, when we mean all of these kinds of objects we speak of
   <quote>relations</quote>.  Not all of <structname>pg_class</structname>'s
   columns are meaningful for all relation kinds.
  </para>

  <table>
   <title><structname>pg_class</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relname</structfield> <type>name</type>
      </para>
      <para>
       Name of the table, index, view, etc.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this relation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>reltype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the data type that corresponds to this table's row type,
       if any; zero for indexes, sequences, and toast tables, which have
       no <structname>pg_type</structname> entry
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>reloftype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       For typed tables, the OID of the underlying composite type;
       zero for all other relations
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the relation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relam</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-am"><structname>pg_am</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If this is a table or an index, the access method used (heap,
       B-tree, hash, etc.); otherwise zero (zero occurs for sequences,
       as well as relations without storage, such as views)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relfilenode</structfield> <type>oid</type>
      </para>
      <para>
       Name of the on-disk file of this relation; zero means this
       is a <quote>mapped</quote> relation whose disk file name is determined
       by low-level state
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>reltablespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The tablespace in which this relation is stored.
       If zero, the database's default tablespace is implied.
       Not meaningful if the relation has no on-disk file,
       except for partitioned tables, where this is the tablespace
       in which partitions will be created when one is not
       specified in the creation command.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relpages</structfield> <type>int4</type>
      </para>
      <para>
       Size of the on-disk representation of this table in pages (of size
       <symbol>BLCKSZ</symbol>).  This is only an estimate used by the
       planner.  It is updated by <link linkend="sql-vacuum"><command>VACUUM</command></link>,
       <link linkend="sql-analyze"><command>ANALYZE</command></link>, and a few DDL commands such as
       <link linkend="sql-createindex"><command>CREATE INDEX</command></link>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>reltuples</structfield> <type>float4</type>
      </para>
      <para>
       Number of live rows in the table.  This is only an estimate used by
       the planner.  It is updated by <link linkend="sql-vacuum"><command>VACUUM</command></link>,
       <link linkend="sql-analyze"><command>ANALYZE</command></link>, and a few DDL commands such as
       <link linkend="sql-createindex"><command>CREATE INDEX</command></link>.
       If the table has never yet been vacuumed or
       analyzed, <structfield>reltuples</structfield>
       contains <literal>-1</literal> indicating that the row count is
       unknown.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relallvisible</structfield> <type>int4</type>
      </para>
      <para>
       Number of pages that are marked all-visible in the table's
       visibility map.  This is only an estimate used by the
       planner.  It is updated by <link linkend="sql-vacuum"><command>VACUUM</command></link>,
       <link linkend="sql-analyze"><command>ANALYZE</command></link>, and a few DDL commands such as
       <link linkend="sql-createindex"><command>CREATE INDEX</command></link>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>reltoastrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the TOAST table associated with this table, zero if none.  The
       TOAST table stores large attributes <quote>out of line</quote> in a
       secondary table.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relhasindex</structfield> <type>bool</type>
      </para>
      <para>
       True if this is a table and it has (or recently had) any indexes
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relisshared</structfield> <type>bool</type>
      </para>
      <para>
       True if this table is shared across all databases in the cluster.  Only
       certain system catalogs (such as <link linkend="catalog-pg-database"><structname>pg_database</structname></link>)
       are shared.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relpersistence</structfield> <type>char</type>
      </para>
      <para>
       <literal>p</literal> = permanent table/sequence, <literal>u</literal> = unlogged table/sequence,
       <literal>t</literal> = temporary table/sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relkind</structfield> <type>char</type>
      </para>
      <para>
       <literal>r</literal> = ordinary table,
       <literal>i</literal> = index,
       <literal>S</literal> = sequence,
       <literal>t</literal> = TOAST table,
       <literal>v</literal> = view,
       <literal>m</literal> = materialized view,
       <literal>c</literal> = composite type,
       <literal>f</literal> = foreign table,
       <literal>p</literal> = partitioned table,
       <literal>I</literal> = partitioned index
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relnatts</structfield> <type>int2</type>
      </para>
      <para>
       Number of user columns in the relation (system columns not
       counted).  There must be this many corresponding entries in
       <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.  See also
       <structname>pg_attribute</structname>.<structfield>attnum</structfield>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relchecks</structfield> <type>int2</type>
      </para>
      <para>
       Number of <literal>CHECK</literal> constraints on the table; see
       <link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link> catalog
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relhasrules</structfield> <type>bool</type>
      </para>
      <para>
       True if table has (or once had) rules; see
       <link linkend="catalog-pg-rewrite"><structname>pg_rewrite</structname></link> catalog
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relhastriggers</structfield> <type>bool</type>
      </para>
      <para>
       True if table has (or once had) triggers; see
       <link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link> catalog
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relhassubclass</structfield> <type>bool</type>
      </para>
      <para>
       True if table or index has (or once had) any inheritance children or partitions
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relrowsecurity</structfield> <type>bool</type>
      </para>
      <para>
       True if table has row-level security enabled; see
       <link linkend="catalog-pg-policy"><structname>pg_policy</structname></link> catalog
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relforcerowsecurity</structfield> <type>bool</type>
      </para>
      <para>
       True if row-level security (when enabled) will also apply to table owner; see
       <link linkend="catalog-pg-policy"><structname>pg_policy</structname></link> catalog
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relispopulated</structfield> <type>bool</type>
      </para>
      <para>
       True if relation is populated (this is true for all
       relations other than some materialized views)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relreplident</structfield> <type>char</type>
      </para>
      <para>
       Columns used to form <quote>replica identity</quote> for rows:
       <literal>d</literal> = default (primary key, if any),
       <literal>n</literal> = nothing,
       <literal>f</literal> = all columns,
       <literal>i</literal> = index with
       <structfield>indisreplident</structfield> set (same as nothing if the
       index used has been dropped)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relispartition</structfield> <type>bool</type>
      </para>
      <para>
       True if table or index is a partition
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relrewrite</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       For new relations being written during a DDL operation that requires a
       table rewrite, this contains the OID of the original relation;
       otherwise zero.  That state is only visible internally; this field should
       never contain anything other than zero for a user-visible relation.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relfrozenxid</structfield> <type>xid</type>
      </para>
      <para>
       All transaction IDs before this one have been replaced with a permanent
       (<quote>frozen</quote>) transaction ID in this table.  This is used to track
       whether the table needs to be vacuumed in order to prevent transaction
       ID wraparound or to allow <literal>pg_xact</literal> to be shrunk.  Zero
       (<symbol>InvalidTransactionId</symbol>) if the relation is not a table.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relminmxid</structfield> <type>xid</type>
      </para>
      <para>
       All multixact IDs before this one have been replaced by a
       transaction ID in this table.  This is used to track
       whether the table needs to be vacuumed in order to prevent multixact ID
       wraparound or to allow <literal>pg_multixact</literal> to be shrunk.  Zero
       (<symbol>InvalidMultiXactId</symbol>) if the relation is not a table.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>reloptions</structfield> <type>text[]</type>
      </para>
      <para>
       Access-method-specific options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>relpartbound</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       If table is a partition (see <structfield>relispartition</structfield>),
       internal representation of the partition bound
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   Several of the Boolean flags in <structname>pg_class</structname> are maintained
   lazily: they are guaranteed to be true if that's the correct state, but
   may not be reset to false immediately when the condition is no longer
   true.  For example, <structfield>relhasindex</structfield> is set by
   <link linkend="sql-createindex"><command>CREATE INDEX</command></link>, but it is never cleared by
   <link linkend="sql-dropindex"><command>DROP INDEX</command></link>.  Instead, <link linkend="sql-vacuum"><command>VACUUM</command></link> clears
   <structfield>relhasindex</structfield> if it finds the table has no indexes.  This
   arrangement avoids race conditions and improves concurrency.
  </para>
 </sect1>

 <sect1 id="catalog-pg-collation">
  <title><structname>pg_collation</structname></title>

  <indexterm zone="catalog-pg-collation">
   <primary>pg_collation</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_collation</structname> describes the
   available collations, which are essentially mappings from an SQL
   name to operating system locale categories.
   See <xref linkend="collation"/> for more information.
  </para>

  <table>
   <title><structname>pg_collation</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collname</structfield> <type>name</type>
      </para>
      <para>
       Collation name (unique per namespace and encoding)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this collation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the collation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collprovider</structfield> <type>char</type>
      </para>
      <para>
       Provider of the collation: <literal>d</literal> = database
       default, <literal>c</literal> = libc, <literal>i</literal> = icu
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collisdeterministic</structfield> <type>bool</type>
      </para>
      <para>
       Is the collation deterministic?
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collencoding</structfield> <type>int4</type>
      </para>
      <para>
       Encoding in which the collation is applicable, or -1 if it
       works for any encoding
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collcollate</structfield> <type>text</type>
      </para>
      <para>
       <symbol>LC_COLLATE</symbol> for this collation object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collctype</structfield> <type>text</type>
      </para>
      <para>
       <symbol>LC_CTYPE</symbol> for this collation object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>colliculocale</structfield> <type>text</type>
      </para>
      <para>
       ICU locale ID for this collation object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>collversion</structfield> <type>text</type>
      </para>
      <para>
       Provider-specific version of the collation.  This is recorded when the
       collation is created and then checked when it is used, to detect
       changes in the collation definition that could lead to data corruption.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   Note that the unique key on this catalog is (<structfield>collname</structfield>,
   <structfield>collencoding</structfield>, <structfield>collnamespace</structfield>) not just
   (<structfield>collname</structfield>, <structfield>collnamespace</structfield>).
   <productname>PostgreSQL</productname> generally ignores all
   collations that do not have <structfield>collencoding</structfield> equal to
   either the current database's encoding or -1, and creation of new entries
   with the same name as an entry with <structfield>collencoding</structfield> = -1
   is forbidden.  Therefore it is sufficient to use a qualified SQL name
   (<replaceable>schema</replaceable>.<replaceable>name</replaceable>) to identify a collation,
   even though this is not unique according to the catalog definition.
   The reason for defining the catalog this way is that
   <application>initdb</application> fills it in at cluster initialization time with
   entries for all locales available on the system, so it must be able to
   hold entries for all encodings that might ever be used in the cluster.
  </para>

  <para>
   In the <literal>template0</literal> database, it could be useful to create
   collations whose encoding does not match the database encoding,
   since they could match the encodings of databases later cloned from
   <literal>template0</literal>.  This would currently have to be done manually.
  </para>
 </sect1>

 <sect1 id="catalog-pg-constraint">
  <title><structname>pg_constraint</structname></title>

  <indexterm zone="catalog-pg-constraint">
   <primary>pg_constraint</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_constraint</structname> stores check, primary
   key, unique, foreign key, and exclusion constraints on tables.
   (Column constraints are not treated specially.  Every column constraint is
   equivalent to some table constraint.)
   Not-null constraints are represented in the
   <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>
   catalog, not here.
  </para>

  <para>
   User-defined constraint triggers (created with <link linkend="sql-createtrigger">
   <command>CREATE CONSTRAINT TRIGGER</command></link>) also give rise to an entry in this table.
  </para>

  <para>
   Check constraints on domains are stored here, too.
  </para>

  <table>
   <title><structname>pg_constraint</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conname</structfield> <type>name</type>
      </para>
      <para>
       Constraint name (not necessarily unique!)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>connamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this constraint
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>contype</structfield> <type>char</type>
      </para>
      <para>
       <literal>c</literal> = check constraint,
       <literal>f</literal> = foreign key constraint,
       <literal>p</literal> = primary key constraint,
       <literal>u</literal> = unique constraint,
       <literal>t</literal> = constraint trigger,
       <literal>x</literal> = exclusion constraint
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>condeferrable</structfield> <type>bool</type>
      </para>
      <para>
       Is the constraint deferrable?
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>condeferred</structfield> <type>bool</type>
      </para>
      <para>
       Is the constraint deferred by default?
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>convalidated</structfield> <type>bool</type>
      </para>
      <para>
       Has the constraint been validated?
       Currently, can be false only for foreign keys and CHECK constraints
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table this constraint is on; zero if not a table constraint
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>contypid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The domain this constraint is on; zero if not a domain constraint
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conindid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The index supporting this constraint, if it's a unique, primary
       key, foreign key, or exclusion constraint; else zero
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conparentid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The corresponding constraint of the parent partitioned table,
       if this is a constraint on a partition; else zero
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>confrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If a foreign key, the referenced table; else zero
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>confupdtype</structfield> <type>char</type>
      </para>
      <para>
       Foreign key update action code:
       <literal>a</literal> = no action,
       <literal>r</literal> = restrict,
       <literal>c</literal> = cascade,
       <literal>n</literal> = set null,
       <literal>d</literal> = set default
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>confdeltype</structfield> <type>char</type>
      </para>
      <para>
       Foreign key deletion action code:
       <literal>a</literal> = no action,
       <literal>r</literal> = restrict,
       <literal>c</literal> = cascade,
       <literal>n</literal> = set null,
       <literal>d</literal> = set default
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>confmatchtype</structfield> <type>char</type>
      </para>
      <para>
       Foreign key match type:
       <literal>f</literal> = full,
       <literal>p</literal> = partial,
       <literal>s</literal> = simple
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conislocal</structfield> <type>bool</type>
      </para>
      <para>
       This constraint is defined locally for the relation.  Note that a
       constraint can be locally defined and inherited simultaneously.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>coninhcount</structfield> <type>int4</type>
      </para>
      <para>
       The number of direct inheritance ancestors this constraint has.
       A constraint with
       a nonzero number of ancestors cannot be dropped nor renamed.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>connoinherit</structfield> <type>bool</type>
      </para>
      <para>
       This constraint is defined locally for the relation.  It is a
       non-inheritable constraint.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conkey</structfield> <type>int2[]</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       If a table constraint (including foreign keys, but not constraint
       triggers), list of the constrained columns
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>confkey</structfield> <type>int2[]</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       If a foreign key, list of the referenced columns
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conpfeqop</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If a foreign key, list of the equality operators for PK = FK comparisons
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conppeqop</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If a foreign key, list of the equality operators for PK = PK comparisons
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conffeqop</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If a foreign key, list of the equality operators for FK = FK comparisons
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>confdelsetcols</structfield> <type>int2[]</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       If a foreign key with a <literal>SET NULL</literal> or <literal>SET
       DEFAULT</literal> delete action, the columns that will be updated.
       If null, all of the referencing columns will be updated.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conexclop</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If an exclusion constraint, list of the per-column exclusion operators
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conbin</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       If a check constraint, an internal representation of the
       expression.  (It's recommended to use
       <function>pg_get_constraintdef()</function> to extract the definition of
       a check constraint.)
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   In the case of an exclusion constraint, <structfield>conkey</structfield>
   is only useful for constraint elements that are simple column references.
   For other cases, a zero appears in <structfield>conkey</structfield>
   and the associated index must be consulted to discover the expression
   that is constrained.  (<structfield>conkey</structfield> thus has the
   same contents as <link linkend="catalog-pg-index"><structname>pg_index</structname></link>.<structfield>indkey</structfield> for the
   index.)
  </para>

  <note>
   <para>
    <literal>pg_class.relchecks</literal> needs to agree with the
    number of check-constraint entries found in this table for each
    relation.
   </para>
  </note>
 </sect1>


 <sect1 id="catalog-pg-conversion">
  <title><structname>pg_conversion</structname></title>

  <indexterm zone="catalog-pg-conversion">
   <primary>pg_conversion</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_conversion</structname> describes
   encoding conversion functions.  See <xref linkend="sql-createconversion"/>
   for more information.
  </para>

  <table>
   <title><structname>pg_conversion</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conname</structfield> <type>name</type>
      </para>
      <para>
       Conversion name (unique within a namespace)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>connamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this conversion
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the conversion
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conforencoding</structfield> <type>int4</type>
      </para>
      <para>
       Source encoding ID (<link linkend="pg-encoding-to-char"><function>pg_encoding_to_char()</function></link>
       can translate this number to the encoding name)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>contoencoding</structfield> <type>int4</type>
      </para>
      <para>
       Destination encoding ID (<link linkend="pg-encoding-to-char"><function>pg_encoding_to_char()</function></link>
       can translate this number to the encoding name)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>conproc</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Conversion function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>condefault</structfield> <type>bool</type>
      </para>
      <para>
       True if this is the default conversion
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>

 <sect1 id="catalog-pg-database">
  <title><structname>pg_database</structname></title>

  <indexterm zone="catalog-pg-database">
   <primary>pg_database</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_database</structname> stores information about
   the available databases.  Databases are created with the <link
   linkend="sql-createdatabase"><command>CREATE DATABASE</command></link> command.
   Consult <xref linkend="managing-databases"/> for details about the meaning
   of some of the parameters.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_database</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_database</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_database</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datname</structfield> <type>name</type>
      </para>
      <para>
       Database name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datdba</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the database, usually the user who created it
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>encoding</structfield> <type>int4</type>
      </para>
      <para>
       Character encoding for this database
       (<link linkend="pg-encoding-to-char"><function>pg_encoding_to_char()</function></link> can translate
       this number to the encoding name)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datlocprovider</structfield> <type>char</type>
      </para>
      <para>
       Locale provider for this database: <literal>c</literal> = libc,
       <literal>i</literal> = icu
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datistemplate</structfield> <type>bool</type>
      </para>
      <para>
       If true, then this database can be cloned by
       any user with <literal>CREATEDB</literal> privileges;
       if false, then only superusers or the owner of
       the database can clone it.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datallowconn</structfield> <type>bool</type>
      </para>
      <para>
       If false then no one can connect to this database.  This is
       used to protect the <literal>template0</literal> database from being altered.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datconnlimit</structfield> <type>int4</type>
      </para>
      <para>
       Sets maximum number of concurrent connections that can be made
       to this database.  -1 means no limit, -2 indicates the database is
       invalid.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datfrozenxid</structfield> <type>xid</type>
      </para>
      <para>
       All transaction IDs before this one have been replaced with a permanent
       (<quote>frozen</quote>) transaction ID in this database.  This is used to
       track whether the database needs to be vacuumed in order to prevent
       transaction ID wraparound or to allow <literal>pg_xact</literal> to be shrunk.
       It is the minimum of the per-table
       <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>relfrozenxid</structfield> values.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datminmxid</structfield> <type>xid</type>
      </para>
      <para>
       All multixact IDs before this one have been replaced with a
       transaction ID in this database.  This is used to
       track whether the database needs to be vacuumed in order to prevent
       multixact ID wraparound or to allow <literal>pg_multixact</literal> to be shrunk.
       It is the minimum of the per-table
       <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>relminmxid</structfield> values.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>dattablespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-tablespace"><structname>pg_tablespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The default tablespace for the database.
       Within this database, all tables for which
       <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>reltablespace</structfield> is zero
       will be stored in this tablespace; in particular, all the non-shared
       system catalogs will be there.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datcollate</structfield> <type>text</type>
      </para>
      <para>
       LC_COLLATE for this database
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datctype</structfield> <type>text</type>
      </para>
      <para>
       LC_CTYPE for this database
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>daticulocale</structfield> <type>text</type>
      </para>
      <para>
       ICU locale ID for this database
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datcollversion</structfield> <type>text</type>
      </para>
      <para>
       Provider-specific version of the collation.  This is recorded when the
       database is created and then checked when it is used, to detect
       changes in the collation definition that could lead to data corruption.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>datacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-db-role-setting">
  <title><structname>pg_db_role_setting</structname></title>

  <indexterm zone="catalog-pg-db-role-setting">
   <primary>pg_db_role_setting</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_db_role_setting</structname> records the default
   values that have been set for run-time configuration variables,
   for each role and database combination.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_db_role_setting</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_db_role_setting</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_db_role_setting</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>setdatabase</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-database"><structname>pg_database</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the database the setting is applicable to, or zero if not database-specific
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>setrole</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the role the setting is applicable to, or zero if not role-specific
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>setconfig</structfield> <type>text[]</type>
      </para>
      <para>
       Defaults for run-time configuration variables
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-default-acl">
  <title><structname>pg_default_acl</structname></title>

  <indexterm zone="catalog-pg-default-acl">
   <primary>pg_default_acl</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_default_acl</structname> stores initial
   privileges to be assigned to newly created objects.
  </para>

  <table>
   <title><structname>pg_default_acl</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>defaclrole</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the role associated with this entry
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>defaclnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace associated with this entry,
       or zero if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>defaclobjtype</structfield> <type>char</type>
      </para>
      <para>
       Type of object this entry is for:
       <literal>r</literal> = relation (table, view),
       <literal>S</literal> = sequence,
       <literal>f</literal> = function,
       <literal>T</literal> = type,
       <literal>n</literal> = schema
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>defaclacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges that this type of object should have on creation
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   A <structname>pg_default_acl</structname> entry shows the initial privileges to
   be assigned to an object belonging to the indicated user.  There are
   currently two types of entry: <quote>global</quote> entries with
   <structfield>defaclnamespace</structfield> = zero, and <quote>per-schema</quote> entries
   that reference a particular schema.  If a global entry is present then
   it <emphasis>overrides</emphasis> the normal hard-wired default privileges
   for the object type.  A per-schema entry, if present, represents privileges
   to be <emphasis>added to</emphasis> the global or hard-wired default privileges.
  </para>

  <para>
   Note that when an ACL entry in another catalog is null, it is taken
   to represent the hard-wired default privileges for its object,
   <emphasis>not</emphasis> whatever might be in <structname>pg_default_acl</structname>
   at the moment.  <structname>pg_default_acl</structname> is only consulted during
   object creation.
  </para>

 </sect1>


 <sect1 id="catalog-pg-depend">
  <title><structname>pg_depend</structname></title>

  <indexterm zone="catalog-pg-depend">
   <primary>pg_depend</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_depend</structname> records the dependency
   relationships between database objects.  This information allows
   <command>DROP</command> commands to find which other objects must be dropped
   by <command>DROP CASCADE</command> or prevent dropping in the <command>DROP
   RESTRICT</command> case.
  </para>

  <para>
   See also <link linkend="catalog-pg-shdepend"><structname>pg_shdepend</structname></link>,
   which performs a similar function for dependencies involving objects
   that are shared across a database cluster.
  </para>

  <table>
   <title><structname>pg_depend</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>classid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog the dependent object is in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the specific dependent object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objsubid</structfield> <type>int4</type>
      </para>
      <para>
       For a table column, this is the column number (the
       <structfield>objid</structfield> and <structfield>classid</structfield> refer to the
       table itself).  For all other object types, this column is
       zero.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>refclassid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog the referenced object is in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>refobjid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the specific referenced object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>refobjsubid</structfield> <type>int4</type>
      </para>
      <para>
       For a table column, this is the column number (the
       <structfield>refobjid</structfield> and <structfield>refclassid</structfield> refer
       to the table itself).  For all other object types, this column
       is zero.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>deptype</structfield> <type>char</type>
      </para>
      <para>
       A code defining the specific semantics of this dependency relationship; see text
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   In all cases, a <structname>pg_depend</structname> entry indicates that the
   referenced object cannot be dropped without also dropping the dependent
   object.  However, there are several subflavors identified by
   <structfield>deptype</structfield>:

   <variablelist>
    <varlistentry>
     <term><symbol>DEPENDENCY_NORMAL</symbol> (<literal>n</literal>)</term>
     <listitem>
      <para>
       A normal relationship between separately-created objects.  The
       dependent object can be dropped without affecting the
       referenced object.  The referenced object can only be dropped
       by specifying <literal>CASCADE</literal>, in which case the dependent
       object is dropped, too.  Example: a table column has a normal
       dependency on its data type.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_AUTO</symbol> (<literal>a</literal>)</term>
     <listitem>
      <para>
       The dependent object can be dropped separately from the
       referenced object, and should be automatically dropped
       (regardless of <literal>RESTRICT</literal> or <literal>CASCADE</literal>
       mode) if the referenced object is dropped.  Example: a named
       constraint on a table is made auto-dependent on the table, so
       that it will go away if the table is dropped.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_INTERNAL</symbol> (<literal>i</literal>)</term>
     <listitem>
      <para>
       The dependent object was created as part of creation of the
       referenced object, and is really just a part of its internal
       implementation.  A direct <command>DROP</command> of the dependent
       object will be disallowed outright (we'll tell the user to issue
       a <command>DROP</command> against the referenced object, instead).
       A <command>DROP</command> of the referenced object will result in
       automatically dropping the dependent object
       whether <literal>CASCADE</literal> is specified or not.  If the
       dependent object has to be dropped due to a dependency on some other
       object being removed, its drop is converted to a drop of the referenced
       object, so that <literal>NORMAL</literal> and <literal>AUTO</literal>
       dependencies of the dependent object behave much like they were
       dependencies of the referenced object.
       Example: a view's <literal>ON SELECT</literal> rule is made
       internally dependent on the view, preventing it from being dropped
       while the view remains.  Dependencies of the rule (such as tables it
       refers to) act as if they were dependencies of the view.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_PARTITION_PRI</symbol> (<literal>P</literal>)</term>
     <term><symbol>DEPENDENCY_PARTITION_SEC</symbol> (<literal>S</literal>)</term>
     <listitem>
      <para>
       The dependent object was created as part of creation of the
       referenced object, and is really just a part of its internal
       implementation; however, unlike <literal>INTERNAL</literal>,
       there is more than one such referenced object.  The dependent object
       must not be dropped unless at least one of these referenced objects
       is dropped; if any one is, the dependent object should be dropped
       whether or not <literal>CASCADE</literal> is specified.  Also
       unlike <literal>INTERNAL</literal>, a drop of some other object
       that the dependent object depends on does not result in automatic
       deletion of any partition-referenced object.  Hence, if the drop
       does not cascade to at least one of these objects via some other
       path, it will be refused.  (In most cases, the dependent object
       shares all its non-partition dependencies with at least one
       partition-referenced object, so that this restriction does not
       result in blocking any cascaded delete.)
       Primary and secondary partition dependencies behave identically
       except that the primary dependency is preferred for use in error
       messages; hence, a partition-dependent object should have one
       primary partition dependency and one or more secondary partition
       dependencies.
       Note that partition dependencies are made in addition to, not
       instead of, any dependencies the object would normally have.  This
       simplifies <command>ATTACH/DETACH PARTITION</command> operations:
       the partition dependencies need only be added or removed.
       Example: a child partitioned index is made partition-dependent
       on both the partition table it is on and the parent partitioned
       index, so that it goes away if either of those is dropped, but
       not otherwise.  The dependency on the parent index is primary,
       so that if the user tries to drop the child partitioned index,
       the error message will suggest dropping the parent index instead
       (not the table).
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_EXTENSION</symbol> (<literal>e</literal>)</term>
     <listitem>
      <para>
       The dependent object is a member of the <firstterm>extension</firstterm> that is
       the referenced object (see
       <link linkend="catalog-pg-extension"><structname>pg_extension</structname></link>).
       The dependent object can be dropped only via
       <link linkend="sql-dropextension"><command>DROP EXTENSION</command></link> on the referenced object.
       Functionally this dependency type acts the same as
       an <literal>INTERNAL</literal> dependency, but it's kept separate for
       clarity and to simplify <application>pg_dump</application>.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>DEPENDENCY_AUTO_EXTENSION</symbol> (<literal>x</literal>)</term>
     <listitem>
      <para>
       The dependent object is not a member of the extension that is the
       referenced object (and so it should not be ignored
       by <application>pg_dump</application>), but it cannot function
       without the extension and should be auto-dropped if the extension is.
       The dependent object may be dropped on its own as well.
       Functionally this dependency type acts the same as
       an <literal>AUTO</literal> dependency, but it's kept separate for
       clarity and to simplify <application>pg_dump</application>.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>

   Other dependency flavors might be needed in future.
  </para>

  <para>
   Note that it's quite possible for two objects to be linked by more than
   one <structname>pg_depend</structname> entry.  For example, a child
   partitioned index would have both a partition-type dependency on its
   associated partition table, and an auto dependency on each column of
   that table that it indexes.  This sort of situation expresses the union
   of multiple dependency semantics.  A dependent object can be dropped
   without <literal>CASCADE</literal> if any of its dependencies satisfies
   its condition for automatic dropping.  Conversely, all the
   dependencies' restrictions about which objects must be dropped together
   must be satisfied.
  </para>

  <para>
   Most objects created during <application>initdb</application> are
   considered <quote>pinned</quote>, which means that the system itself
   depends on them.  Therefore, they are never allowed to be dropped.
   Also, knowing that pinned objects will not be dropped, the dependency
   mechanism doesn't bother to make <structname>pg_depend</structname>
   entries showing dependencies on them.  Thus, for example, a table
   column of type <type>numeric</type> notionally has
   a <literal>NORMAL</literal> dependency on the <type>numeric</type>
   data type, but no such entry actually appears
   in <structname>pg_depend</structname>.
  </para>

 </sect1>


 <sect1 id="catalog-pg-description">
  <title><structname>pg_description</structname></title>

  <indexterm zone="catalog-pg-description">
   <primary>pg_description</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_description</structname> stores optional descriptions
   (comments) for each database object.  Descriptions can be manipulated
   with the <link linkend="sql-comment"><command>COMMENT</command></link> command and viewed with
   <application>psql</application>'s <literal>\d</literal> commands.
   Descriptions of many built-in system objects are provided in the initial
   contents of <structname>pg_description</structname>.
  </para>

  <para>
   See also <link linkend="catalog-pg-shdescription"><structname>pg_shdescription</structname></link>,
   which performs a similar function for descriptions involving objects that
   are shared across a database cluster.
  </para>

  <table>
   <title><structname>pg_description</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objoid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the object this description pertains to
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>classoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog this object appears in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objsubid</structfield> <type>int4</type>
      </para>
      <para>
       For a comment on a table column, this is the column number (the
       <structfield>objoid</structfield> and <structfield>classoid</structfield> refer to
       the table itself).  For all other object types, this column is
       zero.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>description</structfield> <type>text</type>
      </para>
      <para>
       Arbitrary text that serves as the description of this object
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-enum">
  <title><structname>pg_enum</structname></title>

  <indexterm zone="catalog-pg-enum">
   <primary>pg_enum</primary>
  </indexterm>

  <para>
   The <structname>pg_enum</structname> catalog contains entries
   showing the values and labels for each enum type. The
   internal representation of a given enum value is actually the OID
   of its associated row in <structname>pg_enum</structname>.
  </para>

  <table>
   <title><structname>pg_enum</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>enumtypid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-type"><structname>pg_type</structname></link> entry owning this enum value
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>enumsortorder</structfield> <type>float4</type>
      </para>
      <para>
       The sort position of this enum value within its enum type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>enumlabel</structfield> <type>name</type>
      </para>
      <para>
       The textual label for this enum value
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   The OIDs for <structname>pg_enum</structname> rows follow a special
   rule: even-numbered OIDs are guaranteed to be ordered in the same way
   as the sort ordering of their enum type.  That is, if two even OIDs
   belong to the same enum type, the smaller OID must have the smaller
   <structfield>enumsortorder</structfield> value.  Odd-numbered OID values
   need bear no relationship to the sort order.  This rule allows the
   enum comparison routines to avoid catalog lookups in many common cases.
   The routines that create and alter enum types attempt to assign even
   OIDs to enum values whenever possible.
  </para>

  <para>
   When an enum type is created, its members are assigned sort-order
   positions 1..<replaceable>n</replaceable>.  But members added later might be given
   negative or fractional values of <structfield>enumsortorder</structfield>.
   The only requirement on these values is that they be correctly
   ordered and unique within each enum type.
  </para>
 </sect1>


 <sect1 id="catalog-pg-event-trigger">
  <title><structname>pg_event_trigger</structname></title>

  <indexterm zone="catalog-pg-event-trigger">
   <primary>pg_event_trigger</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_event_trigger</structname> stores event triggers.
   See <xref linkend="event-triggers"/> for more information.
  </para>

  <table>
   <title><structname>pg_event_trigger</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>evtname</structfield> <type>name</type>
      </para>
      <para>
       Trigger name (must be unique)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>evtevent</structfield> <type>name</type>
      </para>
      <para>
       Identifies the event for which this trigger fires
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>evtowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the event trigger
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>evtfoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The function to be called
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>evtenabled</structfield> <type>char</type>
      </para>
      <para>
       Controls in which <xref linkend="guc-session-replication-role"/> modes
       the event trigger fires.
       <literal>O</literal> = trigger fires in <quote>origin</quote> and <quote>local</quote> modes,
       <literal>D</literal> = trigger is disabled,
       <literal>R</literal> = trigger fires in <quote>replica</quote> mode,
       <literal>A</literal> = trigger fires always.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>evttags</structfield> <type>text[]</type>
      </para>
      <para>
       Command tags for which this trigger will fire.  If NULL, the firing
       of this trigger is not restricted on the basis of the command tag.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-extension">
  <title><structname>pg_extension</structname></title>

  <indexterm zone="catalog-pg-extension">
   <primary>pg_extension</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_extension</structname> stores information
   about the installed extensions.  See <xref linkend="extend-extensions"/>
   for details about extensions.
  </para>

  <table>
   <title><structname>pg_extension</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extname</structfield> <type>name</type>
      </para>
      <para>
       Name of the extension
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the extension
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Schema containing the extension's exported objects
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extrelocatable</structfield> <type>bool</type>
      </para>
      <para>
       True if extension can be relocated to another schema
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extversion</structfield> <type>text</type>
      </para>
      <para>
       Version name for the extension
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extconfig</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Array of <type>regclass</type> OIDs for the extension's configuration
       table(s), or <literal>NULL</literal> if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>extcondition</structfield> <type>text[]</type>
      </para>
      <para>
       Array of <literal>WHERE</literal>-clause filter conditions for the
       extension's configuration table(s), or <literal>NULL</literal> if none
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   Note that unlike most catalogs with a <quote>namespace</quote> column,
   <structfield>extnamespace</structfield> is not meant to imply
   that the extension belongs to that schema.  Extension names are never
   schema-qualified.  Rather, <structfield>extnamespace</structfield>
   indicates the schema that contains most or all of the extension's
   objects.  If <structfield>extrelocatable</structfield> is true, then
   this schema must in fact contain all schema-qualifiable objects
   belonging to the extension.
  </para>
 </sect1>


 <sect1 id="catalog-pg-foreign-data-wrapper">
  <title><structname>pg_foreign_data_wrapper</structname></title>

  <indexterm zone="catalog-pg-foreign-data-wrapper">
   <primary>pg_foreign_data_wrapper</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_foreign_data_wrapper</structname> stores
   foreign-data wrapper definitions.  A foreign-data wrapper is the
   mechanism by which external data, residing on foreign servers, is
   accessed.
  </para>

  <table>
   <title><structname>pg_foreign_data_wrapper</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>fdwname</structfield> <type>name</type>
      </para>
      <para>
       Name of the foreign-data wrapper
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>fdwowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the foreign-data wrapper
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>fdwhandler</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       References a handler function that is responsible for
       supplying execution routines for the foreign-data wrapper.
       Zero if no handler is provided
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>fdwvalidator</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       References a validator function that is responsible for
       checking the validity of the options given to the
       foreign-data wrapper, as well as options for foreign servers and user
       mappings using the foreign-data wrapper.  Zero if no validator
       is provided
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>fdwacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>fdwoptions</structfield> <type>text[]</type>
      </para>
      <para>
       Foreign-data wrapper specific options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-foreign-server">
  <title><structname>pg_foreign_server</structname></title>

  <indexterm zone="catalog-pg-foreign-server">
   <primary>pg_foreign_server</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_foreign_server</structname> stores
   foreign server definitions.  A foreign server describes a source
   of external data, such as a remote server.  Foreign
   servers are accessed via foreign-data wrappers.
  </para>

  <table>
   <title><structname>pg_foreign_server</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srvname</structfield> <type>name</type>
      </para>
      <para>
       Name of the foreign server
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srvowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the foreign server
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srvfdw</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-foreign-data-wrapper"><structname>pg_foreign_data_wrapper</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the foreign-data wrapper of this foreign server
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srvtype</structfield> <type>text</type>
      </para>
      <para>
       Type of the server (optional)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srvversion</structfield> <type>text</type>
      </para>
      <para>
       Version of the server (optional)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srvacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srvoptions</structfield> <type>text[]</type>
      </para>
      <para>
       Foreign server specific options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-foreign-table">
  <title><structname>pg_foreign_table</structname></title>

  <indexterm zone="catalog-pg-foreign-table">
   <primary>pg_foreign_table</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_foreign_table</structname> contains
   auxiliary information about foreign tables.  A foreign table is
   primarily represented by a
   <link linkend="catalog-pg-class"><structname>pg_class</structname></link>
   entry, just like a regular table.  Its <structname>pg_foreign_table</structname>
   entry contains the information that is pertinent only to foreign tables
   and not any other kind of relation.
  </para>

  <table>
   <title><structname>pg_foreign_table</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ftrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry for this foreign table
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ftserver</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the foreign server for this foreign table
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ftoptions</structfield> <type>text[]</type>
      </para>
      <para>
       Foreign table options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-index">
  <title><structname>pg_index</structname></title>

  <indexterm zone="catalog-pg-index">
   <primary>pg_index</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_index</structname> contains part of the information
   about indexes.  The rest is mostly in
   <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.
  </para>

  <table>
   <title><structname>pg_index</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indexrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry for this index
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry for the table this index is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indnatts</structfield> <type>int2</type>
      </para>
      <para>
       The total number of columns in the index (duplicates
       <literal>pg_class.relnatts</literal>); this number includes both key and included attributes
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indnkeyatts</structfield> <type>int2</type>
      </para>
      <para>
       The number of <firstterm>key columns</firstterm> in the index,
       not counting any <firstterm>included columns</firstterm>, which are
       merely stored and do not participate in the index semantics
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indisunique</structfield> <type>bool</type>
      </para>
      <para>
       If true, this is a unique index
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indnullsnotdistinct</structfield> <type>bool</type>
      </para>
      <para>
       This value is only used for unique indexes.  If false, this unique
       index will consider null values distinct (so the index can contain
       multiple null values in a column, the default PostgreSQL behavior).  If
       it is true, it will consider null values to be equal (so the index can
       only contain one null value in a column).
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indisprimary</structfield> <type>bool</type>
      </para>
      <para>
       If true, this index represents the primary key of the table
       (<structfield>indisunique</structfield> should always be true when this is true)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indisexclusion</structfield> <type>bool</type>
      </para>
      <para>
       If true, this index supports an exclusion constraint
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indimmediate</structfield> <type>bool</type>
      </para>
      <para>
       If true, the uniqueness check is enforced immediately on
       insertion
       (irrelevant if <structfield>indisunique</structfield> is not true)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indisclustered</structfield> <type>bool</type>
      </para>
      <para>
       If true, the table was last clustered on this index
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indisvalid</structfield> <type>bool</type>
      </para>
      <para>
       If true, the index is currently valid for queries.  False means the
       index is possibly incomplete: it must still be modified by
       <link linkend="sql-insert"><command>INSERT</command></link>/<link linkend="sql-update"><command>UPDATE</command></link> operations, but it cannot safely
       be used for queries. If it is unique, the uniqueness property is not
       guaranteed true either.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indcheckxmin</structfield> <type>bool</type>
      </para>
      <para>
       If true, queries must not use the index until the <structfield>xmin</structfield>
       of this <structname>pg_index</structname> row is below their <symbol>TransactionXmin</symbol>
       event horizon, because the table may contain broken <link linkend="storage-hot">HOT chains</link> with
       incompatible rows that they can see
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indisready</structfield> <type>bool</type>
      </para>
      <para>
       If true, the index is currently ready for inserts.  False means the
       index must be ignored by <link linkend="sql-insert"><command>INSERT</command></link>/<link linkend="sql-update"><command>UPDATE</command></link>
       operations.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indislive</structfield> <type>bool</type>
      </para>
      <para>
       If false, the index is in process of being dropped, and should be
       ignored for all purposes (including HOT-safety decisions)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indisreplident</structfield> <type>bool</type>
      </para>
      <para>
       If true this index has been chosen as <quote>replica identity</quote>
       using <link linkend="sql-altertable-replica-identity"><command>ALTER TABLE ...
       REPLICA IDENTITY USING INDEX ...</command></link>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indkey</structfield> <type>int2vector</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       This is an array of <structfield>indnatts</structfield> values that
       indicate which table columns this index indexes.  For example, a value
       of <literal>1 3</literal> would mean that the first and the third table
       columns make up the index entries.  Key columns come before non-key
       (included) columns.  A zero in this array indicates that the
       corresponding index attribute is an expression over the table columns,
       rather than a simple column reference.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indcollation</structfield> <type>oidvector</type>
       (references <link linkend="catalog-pg-collation"><structname>pg_collation</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       For each column in the index key
       (<structfield>indnkeyatts</structfield> values), this contains the OID
       of the collation to use for the index, or zero if the column is not of
       a collatable data type.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indclass</structfield> <type>oidvector</type>
       (references <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       For each column in the index key
       (<structfield>indnkeyatts</structfield> values), this contains the OID
       of the operator class to use.  See
       <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link> for details.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indoption</structfield> <type>int2vector</type>
      </para>
      <para>
       This is an array of <structfield>indnkeyatts</structfield> values that
       store per-column flag bits.  The meaning of the bits is defined by
       the index's access method.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indexprs</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Expression trees (in <function>nodeToString()</function>
       representation) for index attributes that are not simple column
       references.  This is a list with one element for each zero
       entry in <structfield>indkey</structfield>.  Null if all index attributes
       are simple references.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>indpred</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Expression tree (in <function>nodeToString()</function>
       representation) for partial index predicate.  Null if not a
       partial index.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-inherits">
  <title><structname>pg_inherits</structname></title>

  <indexterm zone="catalog-pg-inherits">
   <primary>pg_inherits</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_inherits</structname> records information about
   table and index inheritance hierarchies.  There is one entry for each direct
   parent-child table or index relationship in the database.  (Indirect
   inheritance can be determined by following chains of entries.)
  </para>

  <table>
   <title><structname>pg_inherits</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>inhrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the child table or index
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>inhparent</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the parent table or index
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>inhseqno</structfield> <type>int4</type>
      </para>
      <para>
       If there is more than one direct parent for a child table (multiple
       inheritance), this number tells the order in which the
       inherited columns are to be arranged.  The count starts at 1.
      </para>
      <para>
       Indexes cannot have multiple inheritance, since they can only inherit
       when using declarative partitioning.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>inhdetachpending</structfield> <type>bool</type>
      </para>
      <para>
       <literal>true</literal> for a partition that is in the process of
       being detached; <literal>false</literal> otherwise.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>

 <sect1 id="catalog-pg-init-privs">
  <title><structname>pg_init_privs</structname></title>

  <indexterm zone="catalog-pg-init-privs">
   <primary>pg_init_privs</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_init_privs</structname> records information about
   the initial privileges of objects in the system.  There is one entry
   for each object in the database which has a non-default (non-NULL)
   initial set of privileges.
  </para>

  <para>
   Objects can have initial privileges either by having those privileges set
   when the system is initialized (by <application>initdb</application>) or when the
   object is created during a <link linkend="sql-createextension"><command>CREATE EXTENSION</command></link> and the
   extension script sets initial privileges using the <link linkend="sql-grant"><command>GRANT</command></link>
   system.  Note that the system will automatically handle recording of the
   privileges during the extension script and that extension authors need
   only use the <command>GRANT</command> and <command>REVOKE</command>
   statements in their script to have the privileges recorded.  The
   <literal>privtype</literal> column indicates if the initial privilege was
   set by <application>initdb</application> or during a
   <command>CREATE EXTENSION</command> command.
  </para>

  <para>
   Objects which have initial privileges set by <application>initdb</application> will
   have entries where <literal>privtype</literal> is
   <literal>'i'</literal>, while objects which have initial privileges set
   by <command>CREATE EXTENSION</command> will have entries where
   <literal>privtype</literal> is <literal>'e'</literal>.
  </para>

  <table>
   <title><structname>pg_init_privs</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objoid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the specific object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>classoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog the object is in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objsubid</structfield> <type>int4</type>
      </para>
      <para>
       For a table column, this is the column number (the
       <structfield>objoid</structfield> and <structfield>classoid</structfield> refer to the
       table itself).  For all other object types, this column is
       zero.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>privtype</structfield> <type>char</type>
      </para>
      <para>
       A code defining the type of initial privilege of this object; see text
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>initprivs</structfield> <type>aclitem[]</type>
      </para>
      <para>
       The initial access privileges; see
       <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-language">
  <title><structname>pg_language</structname></title>

  <indexterm zone="catalog-pg-language">
   <primary>pg_language</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_language</structname> registers
   languages in which you can write functions or stored procedures.
   See <xref linkend="sql-createlanguage"/>
   and <xref linkend="xplang"/> for more information about language handlers.
  </para>

  <table>
   <title><structname>pg_language</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lanname</structfield> <type>name</type>
      </para>
      <para>
       Name of the language
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lanowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the language
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lanispl</structfield> <type>bool</type>
      </para>
      <para>
       This is false for internal languages (such as
       <acronym>SQL</acronym>) and true for user-defined languages.
       Currently, <application>pg_dump</application> still uses this
       to determine which languages need to be dumped, but this might be
       replaced by a different mechanism in the future.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lanpltrusted</structfield> <type>bool</type>
      </para>
      <para>
       True if this is a trusted language, which means that it is believed
       not to grant access to anything outside the normal SQL execution
       environment.  Only superusers can create functions in untrusted
       languages.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lanplcallfoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       For noninternal languages this references the language
       handler, which is a special function that is responsible for
       executing all functions that are written in the particular
       language. Zero for internal languages.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>laninline</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       This references a function that is responsible for executing
       <quote>inline</quote> anonymous code blocks
       (<xref linkend="sql-do"/> blocks).
       Zero if inline blocks are not supported.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lanvalidator</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       This references a language validator function that is responsible
       for checking the syntax and validity of new functions when they
       are created.  Zero if no validator is provided.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lanacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-largeobject">
  <title><structname>pg_largeobject</structname></title>

  <indexterm zone="catalog-pg-largeobject">
   <primary>pg_largeobject</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_largeobject</structname> holds the data making up
   <quote>large objects</quote>.  A large object is identified by an OID
   assigned when it is created.  Each large object is broken into
   segments or <quote>pages</quote> small enough to be conveniently stored as rows
   in <structname>pg_largeobject</structname>.
   The amount of data per page is defined to be <symbol>LOBLKSIZE</symbol> (which is currently
   <literal>BLCKSZ/4</literal>, or typically 2 kB).
  </para>

  <para>
   Prior to <productname>PostgreSQL</productname> 9.0, there was no permission structure
   associated with large objects.  As a result,
   <structname>pg_largeobject</structname> was publicly readable and could be
   used to obtain the OIDs (and contents) of all large objects in the system.
   This is no longer the case; use
   <link linkend="catalog-pg-largeobject-metadata"><structname>pg_largeobject_metadata</structname></link>
   to obtain a list of large object OIDs.
  </para>

  <table>
   <title><structname>pg_largeobject</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>loid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-largeobject-metadata"><structname>pg_largeobject_metadata</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Identifier of the large object that includes this page
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pageno</structfield> <type>int4</type>
      </para>
      <para>
       Page number of this page within its large object
       (counting from zero)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>data</structfield> <type>bytea</type>
      </para>
      <para>
       Actual data stored in the large object.
       This will never be more than <symbol>LOBLKSIZE</symbol> bytes and might be less.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   Each row of <structname>pg_largeobject</structname> holds data
   for one page of a large object, beginning at
   byte offset (<literal>pageno * LOBLKSIZE</literal>) within the object.  The implementation
   allows sparse storage: pages might be missing, and might be shorter than
   <literal>LOBLKSIZE</literal> bytes even if they are not the last page of the object.
   Missing regions within a large object read as zeroes.
  </para>

 </sect1>

 <sect1 id="catalog-pg-largeobject-metadata">
  <title><structname>pg_largeobject_metadata</structname></title>

  <indexterm zone="catalog-pg-largeobject-metadata">
   <primary>pg_largeobject_metadata</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_largeobject_metadata</structname>
   holds metadata associated with large objects.  The actual large object
   data is stored in
   <link linkend="catalog-pg-largeobject"><structname>pg_largeobject</structname></link>.
  </para>

  <table>
   <title><structname>pg_largeobject_metadata</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lomowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the large object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>lomacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-namespace">
  <title><structname>pg_namespace</structname></title>

  <indexterm zone="catalog-pg-namespace">
   <primary>pg_namespace</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_namespace</structname> stores namespaces.
   A namespace is the structure underlying SQL schemas: each namespace
   can have a separate collection of relations, types, etc. without name
   conflicts.
  </para>

  <table>
   <title><structname>pg_namespace</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>nspname</structfield> <type>name</type>
      </para>
      <para>
       Name of the namespace
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>nspowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the namespace
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>nspacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-opclass">
  <title><structname>pg_opclass</structname></title>

  <indexterm zone="catalog-pg-opclass">
   <primary>pg_opclass</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_opclass</structname> defines
   index access method operator classes.  Each operator class defines
   semantics for index columns of a particular data type and a particular
   index access method.  An operator class essentially specifies that a
   particular operator family is applicable to a particular indexable column
   data type.  The set of operators from the family that are actually usable
   with the indexed column are whichever ones accept the column's data type
   as their left-hand input.
  </para>

  <para>
   Operator classes are described at length in <xref linkend="xindex"/>.
  </para>

  <table>
   <title><structname>pg_opclass</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opcmethod</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-am"><structname>pg_am</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Index access method operator class is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opcname</structfield> <type>name</type>
      </para>
      <para>
       Name of this operator class
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opcnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Namespace of this operator class
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opcowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the operator class
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opcfamily</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-opfamily"><structname>pg_opfamily</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Operator family containing the operator class
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opcintype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Data type that the operator class indexes
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opcdefault</structfield> <type>bool</type>
      </para>
      <para>
       True if this operator class is the default for <structfield>opcintype</structfield>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opckeytype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Type of data stored in index, or zero if same as <structfield>opcintype</structfield>
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   An operator class's <structfield>opcmethod</structfield> must match the
   <structfield>opfmethod</structfield> of its containing operator family.
   Also, there must be no more than one <structname>pg_opclass</structname>
   row having <structfield>opcdefault</structfield> true for any given combination of
   <structfield>opcmethod</structfield> and <structfield>opcintype</structfield>.
  </para>

 </sect1>


 <sect1 id="catalog-pg-operator">
  <title><structname>pg_operator</structname></title>

  <indexterm zone="catalog-pg-operator">
   <primary>pg_operator</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_operator</structname> stores information about operators.
   See <xref linkend="sql-createoperator"/>
   and <xref linkend="xoper"/> for more information.
  </para>

  <table>
   <title><structname>pg_operator</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprname</structfield> <type>name</type>
      </para>
      <para>
       Name of the operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the operator
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprkind</structfield> <type>char</type>
      </para>
      <para>
       <literal>b</literal> = infix operator (<quote>both</quote>),
       or <literal>l</literal> = prefix operator (<quote>left</quote>)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprcanmerge</structfield> <type>bool</type>
      </para>
      <para>
       This operator supports merge joins
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprcanhash</structfield> <type>bool</type>
      </para>
      <para>
       This operator supports hash joins
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprleft</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Type of the left operand (zero for a prefix operator)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprright</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Type of the right operand
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprresult</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Type of the result
       (zero for a not-yet-defined <quote>shell</quote> operator)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprcom</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Commutator of this operator (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprnegate</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Negator of this operator (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprcode</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Function that implements this operator
       (zero for a not-yet-defined <quote>shell</quote> operator)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprrest</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Restriction selectivity estimation function for this operator
       (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oprjoin</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Join selectivity estimation function for this operator
       (zero if none)
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-opfamily">
  <title><structname>pg_opfamily</structname></title>

  <indexterm zone="catalog-pg-opfamily">
   <primary>pg_opfamily</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_opfamily</structname> defines operator families.
   Each operator family is a collection of operators and associated
   support routines that implement the semantics specified for a particular
   index access method.  Furthermore, the operators in a family are all
   <quote>compatible</quote>, in a way that is specified by the access method.
   The operator family concept allows cross-data-type operators to be used
   with indexes and to be reasoned about using knowledge of access method
   semantics.
  </para>

  <para>
   Operator families are described at length in <xref linkend="xindex"/>.
  </para>

  <table>
   <title><structname>pg_opfamily</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opfmethod</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-am"><structname>pg_am</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Index access method operator family is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opfname</structfield> <type>name</type>
      </para>
      <para>
       Name of this operator family
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opfnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Namespace of this operator family
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>opfowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the operator family
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   The majority of the information defining an operator family is not in its
   <structname>pg_opfamily</structname> row, but in the associated rows in
   <link linkend="catalog-pg-amop"><structname>pg_amop</structname></link>,
   <link linkend="catalog-pg-amproc"><structname>pg_amproc</structname></link>,
   and
   <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.
  </para>

 </sect1>


 <sect1 id="catalog-pg-parameter-acl">
  <title><structname>pg_parameter_acl</structname></title>

  <indexterm zone="catalog-pg-parameter-acl">
   <primary>pg_parameter_acl</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_parameter_acl</structname> records configuration
   parameters for which privileges have been granted to one or more roles.
   No entry is made for parameters that have default privileges.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_parameter_acl</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_parameter_acl</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_parameter_acl</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>parname</structfield> <type>text</type>
      </para>
      <para>
       The name of a configuration parameter for which privileges are granted
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>paracl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>

    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-partitioned-table">
  <title><structname>pg_partitioned_table</structname></title>

  <indexterm zone="catalog-pg-partitioned-table">
   <primary>pg_partitioned_table</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_partitioned_table</structname> stores
   information about how tables are partitioned.
  </para>

  <table>
   <title><structname>pg_partitioned_table</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry for this partitioned table
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partstrat</structfield> <type>char</type>
      </para>
      <para>
       Partitioning strategy; <literal>h</literal> = hash partitioned table,
       <literal>l</literal> = list partitioned table, <literal>r</literal> = range partitioned table
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partnatts</structfield> <type>int2</type>
      </para>
      <para>
       The number of columns in the partition key
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partdefid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry for the default partition
       of this partitioned table, or zero if this partitioned table does not
       have a default partition
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partattrs</structfield> <type>int2vector</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       This is an array of <structfield>partnatts</structfield> values that
       indicate which table columns are part of the partition key.  For
       example, a value of <literal>1 3</literal> would mean that the first
       and the third table columns make up the partition key.  A zero in this
       array indicates that the corresponding partition key column is an
       expression, rather than a simple column reference.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partclass</structfield> <type>oidvector</type>
       (references <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       For each column in the partition key, this contains the OID of the
       operator class to use.  See
       <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link> for details.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partcollation</structfield> <type>oidvector</type>
       (references <link linkend="catalog-pg-collation"><structname>pg_collation</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       For each column in the partition key, this contains the OID of the
       collation to use for partitioning, or zero if the column is not
       of a collatable data type.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>partexprs</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Expression trees (in <function>nodeToString()</function>
       representation) for partition key columns that are not simple column
       references.  This is a list with one element for each zero
       entry in <structfield>partattrs</structfield>.  Null if all partition key columns
       are simple references.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-policy">
  <title><structname>pg_policy</structname></title>

  <indexterm zone="catalog-pg-policy">
   <primary>pg_policy</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_policy</structname> stores row-level
   security policies for tables.  A policy includes the kind of
   command that it applies to (possibly all commands), the roles that it
   applies to, the expression to be added as a security-barrier
   qualification to queries that include the table, and the expression
   to be added as a <literal>WITH CHECK</literal> option for queries that attempt to
   add new records to the table.
  </para>

  <table>
   <title><structname>pg_policy</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>polname</structfield> <type>name</type>
      </para>
      <para>
       The name of the policy
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>polrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table to which the policy applies
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>polcmd</structfield> <type>char</type>
      </para>
      <para>
       The command type to which the policy is applied:
       <literal>r</literal> for <xref linkend="sql-select"/>,
       <literal>a</literal> for <xref linkend="sql-insert"/>,
       <literal>w</literal> for <xref linkend="sql-update"/>,
       <literal>d</literal> for <xref linkend="sql-delete"/>,
       or <literal>*</literal> for all
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>polpermissive</structfield> <type>bool</type>
      </para>
      <para>
       Is the policy permissive or restrictive?
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>polroles</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The roles to which the policy is applied;
       zero means <literal>PUBLIC</literal>
       (and normally appears alone in the array)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>polqual</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       The expression tree to be added to the security barrier qualifications for queries that use the table
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>polwithcheck</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       The expression tree to be added to the WITH CHECK qualifications for queries that attempt to add rows to the table
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <note>
   <para>
    Policies stored in <structname>pg_policy</structname> are applied only when
    <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>relrowsecurity</structfield> is set for
    their table.
   </para>
  </note>

 </sect1>

 <sect1 id="catalog-pg-proc">
  <title><structname>pg_proc</structname></title>

  <indexterm zone="catalog-pg-proc">
   <primary>pg_proc</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_proc</structname> stores information about
   functions, procedures, aggregate functions, and window functions
   (collectively also known as routines).  See <xref
   linkend="sql-createfunction"/>, <xref linkend="sql-createprocedure"/>, and
   <xref linkend="xfunc"/> for more information.
  </para>

  <para>
   If <structfield>prokind</structfield> indicates that the entry is for an
   aggregate function, there should be a matching row in
   <link linkend="catalog-pg-aggregate"><structfield>pg_aggregate</structfield></link>.
  </para>

  <table>
   <title><structname>pg_proc</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proname</structfield> <type>name</type>
      </para>
      <para>
       Name of the function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pronamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prolang</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-language"><structname>pg_language</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Implementation language or call interface of this function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>procost</structfield> <type>float4</type>
      </para>
      <para>
       Estimated execution cost (in units of
       <xref linkend="guc-cpu-operator-cost"/>); if <structfield>proretset</structfield>,
       this is cost per row returned
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prorows</structfield> <type>float4</type>
      </para>
      <para>
       Estimated number of result rows (zero if not <structfield>proretset</structfield>)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>provariadic</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Data type of the variadic array parameter's elements,
       or zero if the function does not have a variadic parameter
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prosupport</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Planner support function for this function
       (see <xref linkend="xfunc-optimization"/>), or zero if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prokind</structfield> <type>char</type>
      </para>
      <para>
       <literal>f</literal> for a normal function, <literal>p</literal>
       for a procedure, <literal>a</literal> for an aggregate function, or
       <literal>w</literal> for a window function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prosecdef</structfield> <type>bool</type>
      </para>
      <para>
       Function is a security definer (i.e., a <quote>setuid</quote>
       function)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proleakproof</structfield> <type>bool</type>
      </para>
      <para>
       The function has no side effects.  No information about the
       arguments is conveyed except via the return value.  Any function
       that might throw an error depending on the values of its arguments
       is not leak-proof.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proisstrict</structfield> <type>bool</type>
      </para>
      <para>
       Function returns null if any call argument is null.  In that
       case the function won't actually be called at all.  Functions
       that are not <quote>strict</quote> must be prepared to handle
       null inputs.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proretset</structfield> <type>bool</type>
      </para>
      <para>
       Function returns a set (i.e., multiple values of the specified
       data type)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>provolatile</structfield> <type>char</type>
      </para>
      <para>
       <structfield>provolatile</structfield> tells whether the function's
       result depends only on its input arguments, or is affected by outside
       factors.
       It is <literal>i</literal> for <quote>immutable</quote> functions,
       which always deliver the same result for the same inputs.
       It is <literal>s</literal> for <quote>stable</quote> functions,
       whose results (for fixed inputs) do not change within a scan.
       It is <literal>v</literal> for <quote>volatile</quote> functions,
       whose results might change at any time.  (Use <literal>v</literal> also
       for functions with side-effects, so that calls to them cannot get
       optimized away.)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proparallel</structfield> <type>char</type>
      </para>
      <para>
       <structfield>proparallel</structfield> tells whether the function
       can be safely run in parallel mode.
       It is <literal>s</literal> for functions which are safe to run in
       parallel mode without restriction.
       It is <literal>r</literal> for functions which can be run in parallel
       mode, but their execution is restricted to the parallel group leader;
       parallel worker processes cannot invoke these functions.
       It is <literal>u</literal> for functions which are unsafe in parallel
       mode; the presence of such a function forces a serial execution plan.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pronargs</structfield> <type>int2</type>
      </para>
      <para>
       Number of input arguments
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pronargdefaults</structfield> <type>int2</type>
      </para>
      <para>
       Number of arguments that have defaults
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prorettype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Data type of the return value
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proargtypes</structfield> <type>oidvector</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       An array of the data types of the function arguments.  This includes
       only input arguments (including <literal>INOUT</literal> and
       <literal>VARIADIC</literal> arguments), and thus represents
       the call signature of the function.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proallargtypes</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       An array of the data types of the function arguments.  This includes
       all arguments (including <literal>OUT</literal> and
       <literal>INOUT</literal> arguments); however, if all the
       arguments are <literal>IN</literal> arguments, this field will be null.
       Note that subscripting is 1-based, whereas for historical reasons
       <structfield>proargtypes</structfield> is subscripted from 0.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proargmodes</structfield> <type>char[]</type>
      </para>
      <para>
       An array of the modes of the function arguments, encoded as
       <literal>i</literal> for <literal>IN</literal> arguments,
       <literal>o</literal> for <literal>OUT</literal> arguments,
       <literal>b</literal> for <literal>INOUT</literal> arguments,
       <literal>v</literal> for <literal>VARIADIC</literal> arguments,
       <literal>t</literal> for <literal>TABLE</literal> arguments.
       If all the arguments are <literal>IN</literal> arguments,
       this field will be null.
       Note that subscripts correspond to positions of
       <structfield>proallargtypes</structfield> not <structfield>proargtypes</structfield>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proargnames</structfield> <type>text[]</type>
      </para>
      <para>
       An array of the names of the function arguments.
       Arguments without a name are set to empty strings in the array.
       If none of the arguments have a name, this field will be null.
       Note that subscripts correspond to positions of
       <structfield>proallargtypes</structfield> not <structfield>proargtypes</structfield>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proargdefaults</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Expression trees (in <function>nodeToString()</function> representation)
       for default values.  This is a list with
       <structfield>pronargdefaults</structfield> elements, corresponding to the last
       <replaceable>N</replaceable> <emphasis>input</emphasis> arguments (i.e., the last
       <replaceable>N</replaceable> <structfield>proargtypes</structfield> positions).
       If none of the arguments have defaults, this field will be null.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>protrftypes</structfield> <type>oid[]</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       An array of the argument/result data type(s) for which to apply
       transforms (from the function's <literal>TRANSFORM</literal>
       clause).  Null if none.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prosrc</structfield> <type>text</type>
      </para>
      <para>
       This tells the function handler how to invoke the function.  It
       might be the actual source code of the function for interpreted
       languages, a link symbol, a file name, or just about anything
       else, depending on the implementation language/call convention.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>probin</structfield> <type>text</type>
      </para>
      <para>
       Additional information about how to invoke the function.
       Again, the interpretation is language-specific.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prosqlbody</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Pre-parsed SQL function body.  This is used for SQL-language
       functions when the body is given in SQL-standard notation
       rather than as a string literal.  It's null in other cases.
       </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proconfig</structfield> <type>text[]</type>
      </para>
      <para>
       Function's local settings for run-time configuration variables
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>proacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   For compiled functions, both built-in and dynamically loaded,
   <structfield>prosrc</structfield> contains the function's C-language
   name (link symbol).
   For SQL-language functions, <structfield>prosrc</structfield> contains
   the function's source text if that is specified as a string literal;
   but if the function body is specified in SQL-standard style,
   <structfield>prosrc</structfield> is unused (typically it's an empty
   string) and <structfield>prosqlbody</structfield> contains the
   pre-parsed definition.
   For all other currently-known language types,
   <structfield>prosrc</structfield> contains the function's source
   text.  <structfield>probin</structfield> is null except for
   dynamically-loaded C functions, for which it gives the name of the
   shared library file containing the function.
  </para>

 </sect1>

 <sect1 id="catalog-pg-publication">
  <title><structname>pg_publication</structname></title>

  <indexterm zone="catalog-pg-publication">
   <primary>pg_publication</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_publication</structname> contains all
   publications created in the database.  For more on publications see
   <xref linkend="logical-replication-publication"/>.
  </para>

  <table>
   <title><structname>pg_publication</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pubname</structfield> <type>name</type>
      </para>
      <para>
       Name of the publication
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pubowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the publication
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>puballtables</structfield> <type>bool</type>
      </para>
      <para>
       If true, this publication automatically includes all tables
       in the database, including any that will be created in the future.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pubinsert</structfield> <type>bool</type>
      </para>
      <para>
       If true, <xref linkend="sql-insert"/> operations are replicated for
       tables in the publication.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pubupdate</structfield> <type>bool</type>
      </para>
      <para>
       If true, <xref linkend="sql-update"/> operations are replicated for
       tables in the publication.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pubdelete</structfield> <type>bool</type>
      </para>
      <para>
       If true, <xref linkend="sql-delete"/> operations are replicated for
       tables in the publication.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pubtruncate</structfield> <type>bool</type>
      </para>
      <para>
       If true, <xref linkend="sql-truncate"/> operations are replicated for
       tables in the publication.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pubviaroot</structfield> <type>bool</type>
      </para>
      <para>
       If true, operations on a leaf partition are replicated using the
       identity and schema of its topmost partitioned ancestor mentioned in the
       publication instead of its own.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-publication-namespace">
  <title><structname>pg_publication_namespace</structname></title>

  <indexterm zone="catalog-pg-publication-namespace">
   <primary>pg_publication_namespace</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_publication_namespace</structname> contains the
   mapping between schemas and publications in the database.  This is a
   many-to-many mapping.
  </para>

  <table>
   <title><structname>pg_publication_namespace</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pnpubid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-publication"><structname>pg_publication</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Reference to publication
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>pnnspid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Reference to schema
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-publication-rel">
  <title><structname>pg_publication_rel</structname></title>

  <indexterm zone="catalog-pg-publication-rel">
   <primary>pg_publication_rel</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_publication_rel</structname> contains the
   mapping between relations and publications in the database.  This is a
   many-to-many mapping.  See also <xref linkend="view-pg-publication-tables"/>
   for a more user-friendly view of this information.
  </para>

  <table>
   <title><structname>pg_publication_rel</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prpubid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-publication"><structname>pg_publication</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Reference to publication
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Reference to relation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
      <structfield>prqual</structfield> <type>pg_node_tree</type>
      </para>
      <para>Expression tree (in <function>nodeToString()</function>
      representation) for the relation's publication qualifying condition. Null
      if there is no publication qualifying condition.</para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prattrs</structfield> <type>int2vector</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       This is an array of values that indicates which table columns are
       part of the publication.  For example, a value of <literal>1 3</literal>
       would mean that the first and the third table columns are published.
       A null value indicates that all columns are published.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-range">
  <title><structname>pg_range</structname></title>

  <indexterm zone="catalog-pg-range">
   <primary>pg_range</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_range</structname> stores information about
   range types.  This is in addition to the types' entries in
   <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.
  </para>

  <table>
   <title><structname>pg_range</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rngtypid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the range type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rngsubtype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the element type (subtype) of this range type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rngmultitypid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the multirange type for this range type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rngcollation</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-collation"><structname>pg_collation</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the collation used for range comparisons, or zero if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rngsubopc</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-opclass"><structname>pg_opclass</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the subtype's operator class used for range comparisons
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rngcanonical</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the function to convert a range value into canonical form,
       or zero if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rngsubdiff</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the function to return the difference between two element
       values as <type>double precision</type>, or zero if none
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   <structfield>rngsubopc</structfield> (plus <structfield>rngcollation</structfield>, if the
   element type is collatable) determines the sort ordering used by the range
   type.  <structfield>rngcanonical</structfield> is used when the element type is
   discrete.  <structfield>rngsubdiff</structfield> is optional but should be supplied to
   improve performance of GiST indexes on the range type.
  </para>

 </sect1>

 <sect1 id="catalog-pg-replication-origin">
  <title><structname>pg_replication_origin</structname></title>

  <indexterm zone="catalog-pg-replication-origin">
   <primary>pg_replication_origin</primary>
  </indexterm>

  <para>
   The <structname>pg_replication_origin</structname> catalog contains
   all replication origins created.  For more on replication origins
   see <xref linkend="replication-origins"/>.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_replication_origin</structname>
   is shared across all databases of a cluster: there is only one copy
   of <structname>pg_replication_origin</structname> per cluster, not one per
   database.
  </para>

  <table>
   <title><structname>pg_replication_origin</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>roident</structfield> <type>oid</type>
      </para>
      <para>
       A unique, cluster-wide identifier for the replication
       origin. Should never leave the system.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>roname</structfield> <type>text</type>
      </para>
      <para>
       The external, user defined, name of a replication
       origin.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-rewrite">
  <title><structname>pg_rewrite</structname></title>

  <indexterm zone="catalog-pg-rewrite">
   <primary>pg_rewrite</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_rewrite</structname> stores rewrite rules for tables and views.
  </para>

  <table>
   <title><structname>pg_rewrite</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>rulename</structfield> <type>name</type>
      </para>
      <para>
       Rule name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ev_class</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table this rule is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ev_type</structfield> <type>char</type>
      </para>
      <para>
       Event type that the rule is for: 1 = <xref linkend="sql-select"/>, 2 =
       <xref linkend="sql-update"/>, 3 = <xref linkend="sql-insert"/>, 4 =
       <xref linkend="sql-delete"/>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ev_enabled</structfield> <type>char</type>
      </para>
      <para>
       Controls in which <xref linkend="guc-session-replication-role"/> modes
       the rule fires.
       <literal>O</literal> = rule fires in <quote>origin</quote> and <quote>local</quote> modes,
       <literal>D</literal> = rule is disabled,
       <literal>R</literal> = rule fires in <quote>replica</quote> mode,
       <literal>A</literal> = rule fires always.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>is_instead</structfield> <type>bool</type>
      </para>
      <para>
       True if the rule is an <literal>INSTEAD</literal> rule
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ev_qual</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Expression tree (in the form of a
       <function>nodeToString()</function> representation) for the
       rule's qualifying condition
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>ev_action</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Query tree (in the form of a
       <function>nodeToString()</function> representation) for the
       rule's action
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <note>
   <para>
    <literal>pg_class.relhasrules</literal>
    must be true if a table has any rules in this catalog.
   </para>
  </note>

 </sect1>

 <sect1 id="catalog-pg-seclabel">
  <title><structname>pg_seclabel</structname></title>

  <indexterm zone="catalog-pg-seclabel">
   <primary>pg_seclabel</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_seclabel</structname> stores security
   labels on database objects.  Security labels can be manipulated
   with the <link linkend="sql-security-label"><command>SECURITY LABEL</command></link> command.  For an easier
   way to view security labels, see <xref linkend="view-pg-seclabels"/>.
  </para>

  <para>
   See also <link linkend="catalog-pg-shseclabel"><structname>pg_shseclabel</structname></link>,
   which performs a similar function for security labels of database objects
   that are shared across a database cluster.
  </para>

  <table>
   <title><structname>pg_seclabel</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objoid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the object this security label pertains to
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>classoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog this object appears in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objsubid</structfield> <type>int4</type>
      </para>
      <para>
       For a security label on a table column, this is the column number (the
       <structfield>objoid</structfield> and <structfield>classoid</structfield> refer to
       the table itself).  For all other object types, this column is
       zero.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>provider</structfield> <type>text</type>
      </para>
      <para>
       The label provider associated with this label.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>label</structfield> <type>text</type>
      </para>
      <para>
       The security label applied to this object.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-sequence">
  <title><structname>pg_sequence</structname></title>

  <indexterm zone="catalog-pg-sequence">
   <primary>pg_sequence</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_sequence</structname> contains information about
   sequences.  Some of the information about sequences, such as the name and
   the schema, is in
   <link linkend="catalog-pg-class"><structname>pg_class</structname></link>
  </para>

  <table>
   <title><structname>pg_sequence</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry for this sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqtypid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Data type of the sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqstart</structfield> <type>int8</type>
      </para>
      <para>
       Start value of the sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqincrement</structfield> <type>int8</type>
      </para>
      <para>
       Increment value of the sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqmax</structfield> <type>int8</type>
      </para>
      <para>
       Maximum value of the sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqmin</structfield> <type>int8</type>
      </para>
      <para>
       Minimum value of the sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqcache</structfield> <type>int8</type>
      </para>
      <para>
       Cache size of the sequence
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>seqcycle</structfield> <type>bool</type>
      </para>
      <para>
       Whether the sequence cycles
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-shdepend">
  <title><structname>pg_shdepend</structname></title>

  <indexterm zone="catalog-pg-shdepend">
   <primary>pg_shdepend</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_shdepend</structname> records the
   dependency relationships between database objects and shared objects,
   such as roles.  This information allows
   <productname>PostgreSQL</productname> to ensure that those objects are
   unreferenced before attempting to delete them.
  </para>

  <para>
   See also <link linkend="catalog-pg-depend"><structname>pg_depend</structname></link>,
   which performs a similar function for dependencies involving objects
   within a single database.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_shdepend</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_shdepend</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_shdepend</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>dbid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-database"><structname>pg_database</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the database the dependent object is in,
       or zero for a shared object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>classid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog the dependent object is in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the specific dependent object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objsubid</structfield> <type>int4</type>
      </para>
      <para>
       For a table column, this is the column number (the
       <structfield>objid</structfield> and <structfield>classid</structfield> refer to the
       table itself).  For all other object types, this column is zero.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>refclassid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog the referenced object is in
       (must be a shared catalog)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>refobjid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the specific referenced object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>deptype</structfield> <type>char</type>
      </para>
      <para>
       A code defining the specific semantics of this dependency relationship; see text
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   In all cases, a <structname>pg_shdepend</structname> entry indicates that
   the referenced object cannot be dropped without also dropping the dependent
   object.  However, there are several subflavors identified by
   <structfield>deptype</structfield>:

   <variablelist>
    <varlistentry>
     <term><symbol>SHARED_DEPENDENCY_OWNER</symbol> (<literal>o</literal>)</term>
     <listitem>
      <para>
       The referenced object (which must be a role) is the owner of the
       dependent object.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>SHARED_DEPENDENCY_ACL</symbol> (<literal>a</literal>)</term>
     <listitem>
      <para>
       The referenced object (which must be a role) is mentioned in the
       ACL (access control list, i.e., privileges list) of the
       dependent object.  (A <symbol>SHARED_DEPENDENCY_ACL</symbol> entry is
       not made for the owner of the object, since the owner will have
       a <symbol>SHARED_DEPENDENCY_OWNER</symbol> entry anyway.)
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>SHARED_DEPENDENCY_POLICY</symbol> (<literal>r</literal>)</term>
     <listitem>
      <para>
       The referenced object (which must be a role) is mentioned as the
       target of a dependent policy object.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term><symbol>SHARED_DEPENDENCY_TABLESPACE</symbol> (<literal>t</literal>)</term>
     <listitem>
      <para>
       The referenced object (which must be a tablespace) is mentioned as
       the tablespace for a relation that doesn't have storage.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>

   Other dependency flavors might be needed in future.  Note in particular
   that the current definition only supports roles and tablespaces as referenced
   objects.
  </para>

  <para>
   As in the <structname>pg_depend</structname> catalog, most objects
   created during <application>initdb</application> are
   considered <quote>pinned</quote>.  No entries are made
   in <structname>pg_shdepend</structname> that would have a pinned
   object as either referenced or dependent object.
  </para>

 </sect1>

 <sect1 id="catalog-pg-shdescription">
  <title><structname>pg_shdescription</structname></title>

  <indexterm zone="catalog-pg-shdescription">
   <primary>pg_shdescription</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_shdescription</structname> stores optional
   descriptions (comments) for shared database objects.  Descriptions can be
   manipulated with the <link linkend="sql-comment"><command>COMMENT</command></link> command and viewed with
   <application>psql</application>'s <literal>\d</literal> commands.
  </para>

  <para>
   See also <link linkend="catalog-pg-description"><structname>pg_description</structname></link>,
   which performs a similar function for descriptions involving objects
   within a single database.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_shdescription</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_shdescription</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_shdescription</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objoid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the object this description pertains to
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>classoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog this object appears in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>description</structfield> <type>text</type>
      </para>
      <para>
       Arbitrary text that serves as the description of this object
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>

 <sect1 id="catalog-pg-shseclabel">
  <title><structname>pg_shseclabel</structname></title>

  <indexterm zone="catalog-pg-shseclabel">
   <primary>pg_shseclabel</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_shseclabel</structname> stores security
   labels on shared database objects.  Security labels can be manipulated
   with the <link linkend="sql-security-label"><command>SECURITY LABEL</command></link> command.  For an easier
   way to view security labels, see <xref linkend="view-pg-seclabels"/>.
  </para>

  <para>
   See also <link linkend="catalog-pg-seclabel"><structname>pg_seclabel</structname></link>,
   which performs a similar function for security labels involving objects
   within a single database.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_shseclabel</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_shseclabel</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_shseclabel</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>objoid</structfield> <type>oid</type>
       (references any OID column)
      </para>
      <para>
       The OID of the object this security label pertains to
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>classoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the system catalog this object appears in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>provider</structfield> <type>text</type>
      </para>
      <para>
       The label provider associated with this label.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>label</structfield> <type>text</type>
      </para>
      <para>
       The security label applied to this object.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-statistic">
  <title><structname>pg_statistic</structname></title>

  <indexterm zone="catalog-pg-statistic">
   <primary>pg_statistic</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_statistic</structname> stores
   statistical data about the contents of the database.  Entries are
   created by <link linkend="sql-analyze"><command>ANALYZE</command></link>
   and subsequently used by the query planner.  Note that all the
   statistical data is inherently approximate, even assuming that it
   is up-to-date.
  </para>

  <para>
   Normally there is one entry, with <structfield>stainherit</structfield> =
   <literal>false</literal>, for each table column that has been analyzed.
   If the table has inheritance children or partitions, a second entry with
   <structfield>stainherit</structfield> = <literal>true</literal> is also created.  This row
   represents the column's statistics over the inheritance tree, i.e.,
   statistics for the data you'd see with
   <literal>SELECT <replaceable>column</replaceable> FROM <replaceable>table</replaceable>*</literal>,
   whereas the <structfield>stainherit</structfield> = <literal>false</literal> row represents
   the results of
   <literal>SELECT <replaceable>column</replaceable> FROM ONLY <replaceable>table</replaceable></literal>.
  </para>

  <para>
   <structname>pg_statistic</structname> also stores statistical data about
   the values of index expressions.  These are described as if they were
   actual data columns; in particular, <structfield>starelid</structfield>
   references the index.  No entry is made for an ordinary non-expression
   index column, however, since it would be redundant with the entry
   for the underlying table column.  Currently, entries for index expressions
   always have <structfield>stainherit</structfield> = <literal>false</literal>.
  </para>

  <para>
   Since different kinds of statistics might be appropriate for different
   kinds of data, <structname>pg_statistic</structname> is designed not
   to assume very much about what sort of statistics it stores.  Only
   extremely general statistics (such as nullness) are given dedicated
   columns in <structname>pg_statistic</structname>.  Everything else
   is stored in <quote>slots</quote>, which are groups of associated columns
   whose content is identified by a code number in one of the slot's columns.
   For more information see
   <filename>src/include/catalog/pg_statistic.h</filename>.
  </para>

  <para>
   <structname>pg_statistic</structname> should not be readable by the
   public, since even statistical information about a table's contents
   might be considered sensitive.  (Example: minimum and maximum values
   of a salary column might be quite interesting.)
   <link linkend="view-pg-stats"><structname>pg_stats</structname></link>
   is a publicly readable view on
   <structname>pg_statistic</structname> that only exposes information
   about those tables that are readable by the current user.
  </para>

  <table>
   <title><structname>pg_statistic</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>starelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table or index that the described column belongs to
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>staattnum</structfield> <type>int2</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       The number of the described column
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stainherit</structfield> <type>bool</type>
      </para>
      <para>
       If true, the stats include values from child tables, not just the
       values in the specified relation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stanullfrac</structfield> <type>float4</type>
      </para>
      <para>
       The fraction of the column's entries that are null
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stawidth</structfield> <type>int4</type>
      </para>
      <para>
       The average stored width, in bytes, of nonnull entries
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stadistinct</structfield> <type>float4</type>
      </para>
      <para>
       The number of distinct nonnull data values in the column.
       A value greater than zero is the actual number of distinct values.
       A value less than zero is the negative of a multiplier for the number
       of rows in the table; for example, a column in which about 80% of the
       values are nonnull and each nonnull value appears about twice on
       average could be represented by <structfield>stadistinct</structfield> = -0.4.
       A zero value means the number of distinct values is unknown.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stakind<replaceable>N</replaceable></structfield> <type>int2</type>
      </para>
      <para>
       A code number indicating the kind of statistics stored in the
       <replaceable>N</replaceable>th <quote>slot</quote> of the
       <structname>pg_statistic</structname> row.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>staop<replaceable>N</replaceable></structfield> <type>oid</type>
       (references <link linkend="catalog-pg-operator"><structname>pg_operator</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       An operator used to derive the statistics stored in the
       <replaceable>N</replaceable>th <quote>slot</quote>.  For example, a
       histogram slot would show the <literal>&lt;</literal> operator
       that defines the sort order of the data.
       Zero if the statistics kind does not require an operator.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stacoll<replaceable>N</replaceable></structfield> <type>oid</type>
       (references <link linkend="catalog-pg-collation"><structname>pg_collation</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The collation used to derive the statistics stored in the
       <replaceable>N</replaceable>th <quote>slot</quote>.  For example, a
       histogram slot for a collatable column would show the collation that
       defines the sort order of the data.  Zero for noncollatable data.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stanumbers<replaceable>N</replaceable></structfield> <type>float4[]</type>
      </para>
      <para>
       Numerical statistics of the appropriate kind for the
       <replaceable>N</replaceable>th <quote>slot</quote>, or null if the slot
       kind does not involve numerical values
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stavalues<replaceable>N</replaceable></structfield> <type>anyarray</type>
      </para>
      <para>
       Column data values of the appropriate kind for the
       <replaceable>N</replaceable>th <quote>slot</quote>, or null if the slot
       kind does not store any data values.  Each array's element
       values are actually of the specific column's data type, or a related
       type such as an array's element type, so there is no way to define
       these columns' type more specifically than <type>anyarray</type>.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>

 <sect1 id="catalog-pg-statistic-ext">
  <title><structname>pg_statistic_ext</structname></title>

  <indexterm zone="catalog-pg-statistic-ext">
   <primary>pg_statistic_ext</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_statistic_ext</structname>
   holds definitions of extended planner statistics.
   Each row in this catalog corresponds to a <firstterm>statistics object</firstterm>
   created with <link linkend="sql-createstatistics"><command>CREATE STATISTICS</command></link>.
  </para>

  <table>
   <title><structname>pg_statistic_ext</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Table containing the columns described by this object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxname</structfield> <type>name</type>
      </para>
      <para>
       Name of the statistics object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this statistics object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the statistics object
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxstattarget</structfield> <type>int4</type>
      </para>
      <para>
       <structfield>stxstattarget</structfield> controls the level of detail
       of statistics accumulated for this statistics object by
       <link linkend="sql-analyze"><command>ANALYZE</command></link>.
       A zero value indicates that no statistics should be collected.
       A negative value says to use the maximum of the statistics targets of
       the referenced columns, if set, or the system default statistics target.
       Positive values of <structfield>stxstattarget</structfield>
       determine the target number of <quote>most common values</quote>
       to collect.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxkeys</structfield> <type>int2vector</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       An array of attribute numbers, indicating which table columns are
       covered by this statistics object;
       for example a value of <literal>1 3</literal> would
       mean that the first and the third table columns are covered
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxkind</structfield> <type>char[]</type>
      </para>
      <para>
       An array containing codes for the enabled statistics kinds;
       valid values are:
       <literal>d</literal> for n-distinct statistics,
       <literal>f</literal> for functional dependency statistics,
       <literal>m</literal> for most common values (MCV) list statistics, and
       <literal>e</literal> for expression statistics
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxexprs</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Expression trees (in <function>nodeToString()</function>
       representation) for statistics object attributes that are not simple
       column references.  This is a list with one element per expression.
       Null if all statistics object attributes are simple references.
      </para></entry>
     </row>

    </tbody>
   </tgroup>
  </table>

  <para>
   The <structname>pg_statistic_ext</structname> entry is filled in
   completely during <link linkend="sql-createstatistics"><command>CREATE STATISTICS</command></link>, but the actual
   statistical values are not computed then.
   Subsequent <link linkend="sql-analyze"><command>ANALYZE</command></link> commands compute the desired values
   and populate an entry in the
   <link linkend="catalog-pg-statistic-ext-data"><structname>pg_statistic_ext_data</structname></link>
   catalog.
  </para>
 </sect1>

 <sect1 id="catalog-pg-statistic-ext-data">
  <title><structname>pg_statistic_ext_data</structname></title>

  <indexterm zone="catalog-pg-statistic-ext">
   <primary>pg_statistic_ext_data</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_statistic_ext_data</structname>
   holds data for extended planner statistics defined in
   <link linkend="catalog-pg-statistic-ext"><structname>pg_statistic_ext</structname></link>.
   Each row in this catalog corresponds to a <firstterm>statistics object</firstterm>
   created with <link linkend="sql-createstatistics"><command>CREATE STATISTICS</command></link>.
  </para>

  <para>
   Normally there is one entry, with <structfield>stxdinherit</structfield> =
   <literal>false</literal>, for each statistics object that has been analyzed.
   If the table has inheritance children or partitions, a second entry with
   <structfield>stxdinherit</structfield> = <literal>true</literal> is also created.
   This row represents the statistics object over the inheritance tree, i.e.,
   statistics for the data you'd see with
   <literal>SELECT * FROM <replaceable>table</replaceable>*</literal>,
   whereas the <structfield>stxdinherit</structfield> = <literal>false</literal> row
   represents the results of
   <literal>SELECT * FROM ONLY <replaceable>table</replaceable></literal>.
  </para>

  <para>
   Like <link linkend="catalog-pg-statistic"><structname>pg_statistic</structname></link>,
   <structname>pg_statistic_ext_data</structname> should not be
   readable by the public, since the contents might be considered sensitive.
   (Example: most common combinations of values in columns might be quite
   interesting.)
   <link linkend="view-pg-stats-ext"><structname>pg_stats_ext</structname></link>
   is a publicly readable view
   on <structname>pg_statistic_ext_data</structname> (after joining
   with <link linkend="catalog-pg-statistic-ext"><structname>pg_statistic_ext</structname></link>) that only exposes
   information about those tables and columns that are readable by the
   current user.
  </para>

  <table>
   <title><structname>pg_statistic_ext_data</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-statistic-ext"><structname>pg_statistic_ext</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Extended statistics object containing the definition for this data
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxdinherit</structfield> <type>bool</type>
      </para>
      <para>
       If true, the stats include values from child tables, not just the
       values in the specified relation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxdndistinct</structfield> <type>pg_ndistinct</type>
      </para>
      <para>
       N-distinct counts, serialized as <structname>pg_ndistinct</structname> type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxddependencies</structfield> <type>pg_dependencies</type>
      </para>
      <para>
       Functional dependency statistics, serialized
       as <structname>pg_dependencies</structname> type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxdmcv</structfield> <type>pg_mcv_list</type>
      </para>
      <para>
       MCV (most-common values) list statistics, serialized as
       <structname>pg_mcv_list</structname> type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>stxdexpr</structfield> <type>pg_statistic[]</type>
      </para>
      <para>
       Per-expression statistics, serialized as an array of
       <structname>pg_statistic</structname> type
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>

 <sect1 id="catalog-pg-subscription">
  <title><structname>pg_subscription</structname></title>

  <indexterm zone="catalog-pg-subscription">
   <primary>pg_subscription</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_subscription</structname> contains all existing
   logical replication subscriptions.  For more information about logical
   replication see <xref linkend="logical-replication"/>.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_subscription</structname> is
   shared across all databases of a cluster: there is only one copy
   of <structname>pg_subscription</structname> per cluster, not one per
   database.
  </para>

  <para>
   Access to the column <structfield>subconninfo</structfield> is revoked from
   normal users, because it could contain plain-text passwords.
  </para>

  <table>
   <title><structname>pg_subscription</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subdbid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-database"><structname>pg_database</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the database that the subscription resides in
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subskiplsn</structfield> <type>pg_lsn</type>
      </para>
      <para>
       Finish LSN of the transaction whose changes are to be skipped, if a valid
       LSN; otherwise <literal>0/0</literal>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subname</structfield> <type>name</type>
      </para>
      <para>
       Name of the subscription
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the subscription
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subenabled</structfield> <type>bool</type>
      </para>
      <para>
       If true, the subscription is enabled and should be replicating
      </para></entry>
     </row>

    <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subbinary</structfield> <type>bool</type>
      </para>
      <para>
       If true, the subscription will request that the publisher send data
       in binary format
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>substream</structfield> <type>bool</type>
      </para>
      <para>
       If true, the subscription will allow streaming of in-progress
       transactions
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subtwophasestate</structfield> <type>char</type>
      </para>
      <para>
       State codes for two-phase mode:
       <literal>d</literal> = disabled,
       <literal>p</literal> = pending enablement,
       <literal>e</literal> = enabled
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subdisableonerr</structfield> <type>bool</type>
      </para>
      <para>
       If true, the subscription will be disabled if one of its workers
       detects an error
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subconninfo</structfield> <type>text</type>
      </para>
      <para>
       Connection string to the upstream database
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subslotname</structfield> <type>name</type>
      </para>
      <para>
       Name of the replication slot in the upstream database (also used
       for the local replication origin name);
       null represents <literal>NONE</literal>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subsynccommit</structfield> <type>text</type>
      </para>
      <para>
       The <varname>synchronous_commit</varname>
       setting for the subscription's workers to use
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>subpublications</structfield> <type>text[]</type>
      </para>
      <para>
       Array of subscribed publication names. These reference
       publications defined in the upstream database. For more on publications
       see <xref linkend="logical-replication-publication"/>.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-subscription-rel">
  <title><structname>pg_subscription_rel</structname></title>

  <indexterm zone="catalog-pg-subscription-rel">
   <primary>pg_subscription_rel</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_subscription_rel</structname> contains the
   state for each replicated relation in each subscription.  This is a
   many-to-many mapping.
  </para>

  <para>
   This catalog only contains tables known to the subscription after running
   either <link linkend="sql-createsubscription"><command>CREATE SUBSCRIPTION</command></link> or
   <link linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ... REFRESH
   PUBLICATION</command></link>.
  </para>

  <table>
   <title><structname>pg_subscription_rel</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srsubid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-subscription"><structname>pg_subscription</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Reference to subscription
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Reference to relation
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srsubstate</structfield> <type>char</type>
      </para>
      <para>
       State code:
       <literal>i</literal> = initialize,
       <literal>d</literal> = data is being copied,
       <literal>f</literal> = finished table copy,
       <literal>s</literal> = synchronized,
       <literal>r</literal> = ready (normal replication)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>srsublsn</structfield> <type>pg_lsn</type>
      </para>
      <para>
       Remote LSN of the state change used for synchronization coordination
       when in <literal>s</literal> or <literal>r</literal> states,
       otherwise null
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="catalog-pg-tablespace">
  <title><structname>pg_tablespace</structname></title>

  <indexterm zone="catalog-pg-tablespace">
   <primary>pg_tablespace</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_tablespace</structname> stores information
   about the available tablespaces.  Tables can be placed in particular
   tablespaces to aid administration of disk layout.
  </para>

  <para>
   Unlike most system catalogs, <structname>pg_tablespace</structname>
   is shared across all databases of a cluster: there is only one
   copy of <structname>pg_tablespace</structname> per cluster, not
   one per database.
  </para>

  <table>
   <title><structname>pg_tablespace</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>spcname</structfield> <type>name</type>
      </para>
      <para>
       Tablespace name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>spcowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the tablespace, usually the user who created it
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>spcacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>spcoptions</structfield> <type>text[]</type>
      </para>
      <para>
       Tablespace-level options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-transform">
  <title><structname>pg_transform</structname></title>

  <indexterm zone="catalog-pg-transform">
   <primary>pg_transform</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_transform</structname> stores information about
   transforms, which are a mechanism to adapt data types to procedural
   languages.  See <xref linkend="sql-createtransform"/> for more information.
  </para>

  <table>
   <title><structname>pg_transform</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>trftype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the data type this transform is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>trflang</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-language"><structname>pg_language</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the language this transform is for
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>trffromsql</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the function to use when converting the data type for input
       to the procedural language (e.g., function parameters).  Zero is stored
       if the default behavior should be used.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>trftosql</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the function to use when converting output from the
       procedural language (e.g., return values) to the data type.  Zero is
       stored if the default behavior should be used.
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-trigger">
  <title><structname>pg_trigger</structname></title>

  <indexterm zone="catalog-pg-trigger">
   <primary>pg_trigger</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_trigger</structname> stores triggers on tables
   and views.
   See <xref linkend="sql-createtrigger"/>
   for more information.
  </para>

  <table>
   <title><structname>pg_trigger</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table this trigger is on
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgparentid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-trigger"><structname>pg_trigger</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Parent trigger that this trigger is cloned from (this happens when
       partitions are created or attached to a partitioned table);
       zero if not a clone
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgname</structfield> <type>name</type>
      </para>
      <para>
       Trigger name (must be unique among triggers of same table)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgfoid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The function to be called
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgtype</structfield> <type>int2</type>
      </para>
      <para>
       Bit mask identifying trigger firing conditions
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgenabled</structfield> <type>char</type>
      </para>
      <para>
       Controls in which <xref linkend="guc-session-replication-role"/> modes
       the trigger fires.
       <literal>O</literal> = trigger fires in <quote>origin</quote> and <quote>local</quote> modes,
       <literal>D</literal> = trigger is disabled,
       <literal>R</literal> = trigger fires in <quote>replica</quote> mode,
       <literal>A</literal> = trigger fires always.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgisinternal</structfield> <type>bool</type>
      </para>
      <para>
       True if trigger is internally generated (usually, to enforce
       the constraint identified by <structfield>tgconstraint</structfield>)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgconstrrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The table referenced by a referential integrity constraint
       (zero if trigger is not for a referential integrity constraint)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgconstrindid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The index supporting a unique, primary key, referential integrity,
       or exclusion constraint
       (zero if trigger is not for one of these types of constraint)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgconstraint</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The <link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link> entry associated with the trigger
       (zero if trigger is not for a constraint)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgdeferrable</structfield> <type>bool</type>
      </para>
      <para>
       True if constraint trigger is deferrable
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tginitdeferred</structfield> <type>bool</type>
      </para>
      <para>
       True if constraint trigger is initially deferred
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgnargs</structfield> <type>int2</type>
      </para>
      <para>
       Number of argument strings passed to trigger function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgattr</structfield> <type>int2vector</type>
       (references <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link>.<structfield>attnum</structfield>)
      </para>
      <para>
       Column numbers, if trigger is column-specific; otherwise an
       empty array
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgargs</structfield> <type>bytea</type>
      </para>
      <para>
       Argument strings to pass to trigger, each NULL-terminated
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgqual</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       Expression tree (in <function>nodeToString()</function>
       representation) for the trigger's <literal>WHEN</literal> condition, or null
       if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgoldtable</structfield> <type>name</type>
      </para>
      <para>
       <literal>REFERENCING</literal> clause name for <literal>OLD TABLE</literal>,
       or null if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tgnewtable</structfield> <type>name</type>
      </para>
      <para>
       <literal>REFERENCING</literal> clause name for <literal>NEW TABLE</literal>,
       or null if none
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <para>
   Currently, column-specific triggering is supported only for
   <literal>UPDATE</literal> events, and so <structfield>tgattr</structfield> is relevant
   only for that event type.  <structfield>tgtype</structfield> might
   contain bits for other event types as well, but those are presumed
   to be table-wide regardless of what is in <structfield>tgattr</structfield>.
  </para>

  <note>
   <para>
    When <structfield>tgconstraint</structfield> is nonzero,
    <structfield>tgconstrrelid</structfield>, <structfield>tgconstrindid</structfield>,
    <structfield>tgdeferrable</structfield>, and <structfield>tginitdeferred</structfield> are
    largely redundant with the referenced <link linkend="catalog-pg-constraint"><structname>pg_constraint</structname></link> entry.
    However, it is possible for a non-deferrable trigger to be associated
    with a deferrable constraint: foreign key constraints can have some
    deferrable and some non-deferrable triggers.
   </para>
  </note>

  <note>
   <para>
    <literal>pg_class.relhastriggers</literal>
    must be true if a relation has any triggers in this catalog.
   </para>
  </note>

 </sect1>


 <sect1 id="catalog-pg-ts-config">
  <title><structname>pg_ts_config</structname></title>

  <indexterm zone="catalog-pg-ts-config">
   <primary>pg_ts_config</primary>
  </indexterm>

  <para>
   The <structname>pg_ts_config</structname> catalog contains entries
   representing text search configurations.  A configuration specifies
   a particular text search parser and a list of dictionaries to use
   for each of the parser's output token types.  The parser is shown
   in the <structname>pg_ts_config</structname> entry, but the
   token-to-dictionary mapping is defined by subsidiary entries in <link
   linkend="catalog-pg-ts-config-map"><structname>pg_ts_config_map</structname></link>.
  </para>

  <para>
   <productname>PostgreSQL</productname>'s text search features are
   described at length in <xref linkend="textsearch"/>.
  </para>

  <table>
   <title><structname>pg_ts_config</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>cfgname</structfield> <type>name</type>
      </para>
      <para>
       Text search configuration name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>cfgnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this configuration
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>cfgowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the configuration
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>cfgparser</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-ts-parser"><structname>pg_ts_parser</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the text search parser for this configuration
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-ts-config-map">
  <title><structname>pg_ts_config_map</structname></title>

  <indexterm zone="catalog-pg-ts-config-map">
   <primary>pg_ts_config_map</primary>
  </indexterm>

  <para>
   The <structname>pg_ts_config_map</structname> catalog contains entries
   showing which text search dictionaries should be consulted, and in
   what order, for each output token type of each text search configuration's
   parser.
  </para>

  <para>
   <productname>PostgreSQL</productname>'s text search features are
   described at length in <xref linkend="textsearch"/>.
  </para>

  <table>
   <title><structname>pg_ts_config_map</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>mapcfg</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-ts-config"><structname>pg_ts_config</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the <link linkend="catalog-pg-ts-config"><structname>pg_ts_config</structname></link> entry owning this map entry
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>maptokentype</structfield> <type>int4</type>
      </para>
      <para>
       A token type emitted by the configuration's parser
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>mapseqno</structfield> <type>int4</type>
      </para>
      <para>
       Order in which to consult this entry (lower
       <structfield>mapseqno</structfield>s first)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>mapdict</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-ts-dict"><structname>pg_ts_dict</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the text search dictionary to consult
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-ts-dict">
  <title><structname>pg_ts_dict</structname></title>

  <indexterm zone="catalog-pg-ts-dict">
   <primary>pg_ts_dict</primary>
  </indexterm>

  <para>
   The <structname>pg_ts_dict</structname> catalog contains entries
   defining text search dictionaries.  A dictionary depends on a text
   search template, which specifies all the implementation functions
   needed; the dictionary itself provides values for the user-settable
   parameters supported by the template.  This division of labor allows
   dictionaries to be created by unprivileged users.  The parameters
   are specified by a text string <structfield>dictinitoption</structfield>,
   whose format and meaning vary depending on the template.
  </para>

  <para>
   <productname>PostgreSQL</productname>'s text search features are
   described at length in <xref linkend="textsearch"/>.
  </para>

  <table>
   <title><structname>pg_ts_dict</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>dictname</structfield> <type>name</type>
      </para>
      <para>
       Text search dictionary name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>dictnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this dictionary
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>dictowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the dictionary
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>dicttemplate</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-ts-template"><structname>pg_ts_template</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the text search template for this dictionary
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>dictinitoption</structfield> <type>text</type>
      </para>
      <para>
       Initialization option string for the template
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-ts-parser">
  <title><structname>pg_ts_parser</structname></title>

  <indexterm zone="catalog-pg-ts-parser">
   <primary>pg_ts_parser</primary>
  </indexterm>

  <para>
   The <structname>pg_ts_parser</structname> catalog contains entries
   defining text search parsers.  A parser is responsible for splitting
   input text into lexemes and assigning a token type to each lexeme.
   Since a parser must be implemented by C-language-level functions,
   creation of new parsers is restricted to database superusers.
  </para>

  <para>
   <productname>PostgreSQL</productname>'s text search features are
   described at length in <xref linkend="textsearch"/>.
  </para>

  <table>
   <title><structname>pg_ts_parser</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prsname</structfield> <type>name</type>
      </para>
      <para>
       Text search parser name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prsnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this parser
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prsstart</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the parser's startup function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prstoken</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the parser's next-token function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prsend</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the parser's shutdown function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prsheadline</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the parser's headline function (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>prslextype</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the parser's lextype function
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-ts-template">
  <title><structname>pg_ts_template</structname></title>

  <indexterm zone="catalog-pg-ts-template">
   <primary>pg_ts_template</primary>
  </indexterm>

  <para>
   The <structname>pg_ts_template</structname> catalog contains entries
   defining text search templates.  A template is the implementation
   skeleton for a class of text search dictionaries.
   Since a template must be implemented by C-language-level functions,
   creation of new templates is restricted to database superusers.
  </para>

  <para>
   <productname>PostgreSQL</productname>'s text search features are
   described at length in <xref linkend="textsearch"/>.
  </para>

  <table>
   <title><structname>pg_ts_template</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tmplname</structfield> <type>name</type>
      </para>
      <para>
       Text search template name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tmplnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this template
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tmplinit</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the template's initialization function (zero if none)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>tmpllexize</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the template's lexize function
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>


 <sect1 id="catalog-pg-type">
  <title><structname>pg_type</structname></title>

  <indexterm zone="catalog-pg-type">
   <primary>pg_type</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_type</structname> stores information about data
   types.  Base types and enum types (scalar types) are created with
   <link linkend="sql-createtype"><command>CREATE TYPE</command></link>, and
   domains with
   <link linkend="sql-createdomain"><command>CREATE DOMAIN</command></link>.
   A composite type is automatically created for each table in the database, to
   represent the row structure of the table.  It is also possible to create
   composite types with <command>CREATE TYPE AS</command>.
  </para>

  <table>
   <title><structname>pg_type</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typname</structfield> <type>name</type>
      </para>
      <para>
       Data type name
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typnamespace</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the namespace that contains this type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typowner</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Owner of the type
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typlen</structfield> <type>int2</type>
      </para>
      <para>
       For a fixed-size type, <structfield>typlen</structfield> is the number
       of bytes in the internal representation of the type.  But for a
       variable-length type, <structfield>typlen</structfield> is negative.
       -1 indicates a <quote>varlena</quote> type (one that has a length word),
       -2 indicates a null-terminated C string.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typbyval</structfield> <type>bool</type>
      </para>
      <para>
       <structfield>typbyval</structfield> determines whether internal
       routines pass a value of this type by value or by reference.
       <structfield>typbyval</structfield> had better be false if
       <structfield>typlen</structfield> is not 1, 2, or 4 (or 8 on machines
       where Datum is 8 bytes).
       Variable-length types are always passed by reference. Note that
       <structfield>typbyval</structfield> can be false even if the
       length would allow pass-by-value.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typtype</structfield> <type>char</type>
      </para>
      <para>
       <structfield>typtype</structfield> is
       <literal>b</literal> for a base type,
       <literal>c</literal> for a composite type (e.g., a table's row type),
       <literal>d</literal> for a domain,
       <literal>e</literal> for an enum type,
       <literal>p</literal> for a pseudo-type,
       <literal>r</literal> for a range type, or
       <literal>m</literal> for a multirange type.
       See also <structfield>typrelid</structfield> and
       <structfield>typbasetype</structfield>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typcategory</structfield> <type>char</type>
      </para>
      <para>
       <structfield>typcategory</structfield> is an arbitrary classification
       of data types that is used by the parser to determine which implicit
       casts should be <quote>preferred</quote>.
       See <xref linkend="catalog-typcategory-table"/>.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typispreferred</structfield> <type>bool</type>
      </para>
      <para>
       True if the type is a preferred cast target within its
       <structfield>typcategory</structfield>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typisdefined</structfield> <type>bool</type>
      </para>
      <para>
       True if the type is defined, false if this is a placeholder
       entry for a not-yet-defined type.  When
       <structfield>typisdefined</structfield> is false, nothing
       except the type name, namespace, and OID can be relied on.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typdelim</structfield> <type>char</type>
      </para>
      <para>
       Character that separates two values of this type when parsing
       array input.  Note that the delimiter is associated with the array
       element data type, not the array data type.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typrelid</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If this is a composite type (see
       <structfield>typtype</structfield>), then this column points to
       the <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry that defines the
       corresponding table.  (For a free-standing composite type, the
       <link linkend="catalog-pg-class"><structname>pg_class</structname></link> entry doesn't really represent
       a table, but it is needed anyway for the type's
       <link linkend="catalog-pg-attribute"><structname>pg_attribute</structname></link> entries to link to.)
       Zero for non-composite types.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typsubscript</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Subscripting handler function's OID, or zero if this type doesn't
       support subscripting.  Types that are <quote>true</quote> array
       types have <structfield>typsubscript</structfield>
       = <function>array_subscript_handler</function>, but other types may
       have other handler functions to implement specialized subscripting
       behavior.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typelem</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If <structfield>typelem</structfield> is not zero then it
       identifies another row in <structname>pg_type</structname>,
       defining the type yielded by subscripting.  This should be zero
       if <structfield>typsubscript</structfield> is zero.  However, it can
       be zero when <structfield>typsubscript</structfield> isn't zero, if the
       handler doesn't need <structfield>typelem</structfield> to
       determine the subscripting result type.
       Note that a <structfield>typelem</structfield> dependency is
       considered to imply physical containment of the element type in
       this type; so DDL changes on the element type might be restricted
       by the presence of this type.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typarray</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If <structfield>typarray</structfield> is not zero then it
       identifies another row in <structname>pg_type</structname>, which
       is the <quote>true</quote> array type having this type as element
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typinput</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Input conversion function (text format)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typoutput</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Output conversion function (text format)
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typreceive</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Input conversion function (binary format), or zero if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typsend</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Output conversion function (binary format), or zero if none
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typmodin</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Type modifier input function, or zero if type does not support modifiers
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typmodout</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Type modifier output function, or zero to use the standard format
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typanalyze</structfield> <type>regproc</type>
       (references <link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       Custom <xref linkend="sql-analyze"/> function,
       or zero to use the standard function
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typalign</structfield> <type>char</type>
      </para>
      <para>
       <structfield>typalign</structfield> is the alignment required
       when storing a value of this type.  It applies to storage on
       disk as well as most representations of the value inside
       <productname>PostgreSQL</productname>.
       When multiple values are stored consecutively, such
       as in the representation of a complete row on disk, padding is
       inserted before a datum of this type so that it begins on the
       specified boundary.  The alignment reference is the beginning
       of the first datum in the sequence.
       Possible values are:
       <itemizedlist>
        <listitem>
         <para><literal>c</literal> = <type>char</type> alignment, i.e., no alignment needed.</para>
        </listitem>
        <listitem>
         <para><literal>s</literal> = <type>short</type> alignment (2 bytes on most machines).</para>
        </listitem>
        <listitem>
         <para><literal>i</literal> = <type>int</type> alignment (4 bytes on most machines).</para>
        </listitem>
        <listitem>
         <para><literal>d</literal> = <type>double</type> alignment (8 bytes on many machines, but by no means all).</para>
        </listitem>
       </itemizedlist>
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typstorage</structfield> <type>char</type>
      </para>
      <para>
       <structfield>typstorage</structfield> tells for varlena
       types (those with <structfield>typlen</structfield> = -1) if
       the type is prepared for toasting and what the default strategy
       for attributes of this type should be.
       Possible values are:
       <itemizedlist>
        <listitem>
         <para>
          <literal>p</literal> (plain): Values must always be stored plain
          (non-varlena types always use this value).
         </para>
        </listitem>
        <listitem>
         <para>
          <literal>e</literal> (external): Values can be stored in a
          secondary <quote>TOAST</quote> relation (if relation has one, see
          <literal>pg_class.reltoastrelid</literal>).
         </para>
        </listitem>
        <listitem>
         <para>
          <literal>m</literal> (main): Values can be compressed and stored
          inline.
         </para>
        </listitem>
        <listitem>
         <para>
          <literal>x</literal> (extended): Values can be compressed and/or
          moved to a secondary relation.
         </para>
        </listitem>
       </itemizedlist>
       <literal>x</literal> is the usual choice for toast-able types.
       Note that <literal>m</literal> values can also be moved out to
       secondary storage, but only as a last resort (<literal>e</literal>
       and <literal>x</literal> values are moved first).
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typnotnull</structfield> <type>bool</type>
      </para>
      <para>
       <structfield>typnotnull</structfield> represents a not-null
       constraint on a type.  Used for domains only.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typbasetype</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-type"><structname>pg_type</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       If this is a domain (see <structfield>typtype</structfield>), then
       <structfield>typbasetype</structfield> identifies the type that this
       one is based on.  Zero if this type is not a domain.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typtypmod</structfield> <type>int4</type>
      </para>
      <para>
       Domains use <structfield>typtypmod</structfield> to record the <literal>typmod</literal>
       to be applied to their base type (-1 if base type does not use a
       <literal>typmod</literal>).  -1 if this type is not a domain.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typndims</structfield> <type>int4</type>
      </para>
      <para>
       <structfield>typndims</structfield> is the number of array dimensions
       for a domain over an array (that is, <structfield>typbasetype</structfield> is
       an array type).
       Zero for types other than domains over array types.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typcollation</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-collation"><structname>pg_collation</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       <structfield>typcollation</structfield> specifies the collation
       of the type.  If the type does not support collations, this will
       be zero.  A base type that supports collations will have a nonzero
       value here, typically <symbol>DEFAULT_COLLATION_OID</symbol>.
       A domain over a collatable type can have a collation OID different
       from its base type's, if one was specified for the domain.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typdefaultbin</structfield> <type>pg_node_tree</type>
      </para>
      <para>
       If <structfield>typdefaultbin</structfield> is not null, it is the
       <function>nodeToString()</function>
       representation of a default expression for the type.  This is
       only used for domains.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typdefault</structfield> <type>text</type>
      </para>
      <para>
       <structfield>typdefault</structfield> is null if the type has no associated
       default value. If <structfield>typdefaultbin</structfield> is not null,
       <structfield>typdefault</structfield> must contain a human-readable version of the
       default expression represented by <structfield>typdefaultbin</structfield>.  If
       <structfield>typdefaultbin</structfield> is null and <structfield>typdefault</structfield> is
       not, then <structfield>typdefault</structfield> is the external representation of
       the type's default value, which can be fed to the type's input
       converter to produce a constant.
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>typacl</structfield> <type>aclitem[]</type>
      </para>
      <para>
       Access privileges; see <xref linkend="ddl-priv"/> for details
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>

  <note>
   <para>
    For fixed-width types used in system tables, it is critical that the size
    and alignment defined in <structname>pg_type</structname>
    agree with the way that the compiler will lay out the column in
    a structure representing a table row.
   </para>
  </note>

  <para>
   <xref linkend="catalog-typcategory-table"/> lists the system-defined values
   of <structfield>typcategory</structfield>.  Any future additions to this list will
   also be upper-case ASCII letters.  All other ASCII characters are reserved
   for user-defined categories.
  </para>

  <table id="catalog-typcategory-table">
   <title><structfield>typcategory</structfield> Codes</title>

   <tgroup cols="2">
    <thead>
     <row>
      <entry>Code</entry>
      <entry>Category</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry><literal>A</literal></entry>
      <entry>Array types</entry>
     </row>
     <row>
      <entry><literal>B</literal></entry>
      <entry>Boolean types</entry>
     </row>
     <row>
      <entry><literal>C</literal></entry>
      <entry>Composite types</entry>
     </row>
     <row>
      <entry><literal>D</literal></entry>
      <entry>Date/time types</entry>
     </row>
     <row>
      <entry><literal>E</literal></entry>
      <entry>Enum types</entry>
     </row>
     <row>
      <entry><literal>G</literal></entry>
      <entry>Geometric types</entry>
     </row>
     <row>
      <entry><literal>I</literal></entry>
      <entry>Network address types</entry>
     </row>
     <row>
      <entry><literal>N</literal></entry>
      <entry>Numeric types</entry>
     </row>
     <row>
      <entry><literal>P</literal></entry>
      <entry>Pseudo-types</entry>
     </row>
     <row>
      <entry><literal>R</literal></entry>
      <entry>Range types</entry>
     </row>
     <row>
      <entry><literal>S</literal></entry>
      <entry>String types</entry>
     </row>
     <row>
      <entry><literal>T</literal></entry>
      <entry>Timespan types</entry>
     </row>
     <row>
      <entry><literal>U</literal></entry>
      <entry>User-defined types</entry>
     </row>
     <row>
      <entry><literal>V</literal></entry>
      <entry>Bit-string types</entry>
     </row>
     <row>
      <entry><literal>X</literal></entry>
      <entry><type>unknown</type> type</entry>
     </row>
     <row>
      <entry><literal>Z</literal></entry>
      <entry>Internal-use types</entry>
     </row>
    </tbody>
   </tgroup>
  </table>

 </sect1>


 <sect1 id="catalog-pg-user-mapping">
  <title><structname>pg_user_mapping</structname></title>

  <indexterm zone="catalog-pg-user-mapping">
   <primary>pg_user_mapping</primary>
  </indexterm>

  <para>
   The catalog <structname>pg_user_mapping</structname> stores
   the mappings from local user to remote.  Access to this catalog is
   restricted from normal users, use the view
   <link linkend="view-pg-user-mappings"><structname>pg_user_mappings</structname></link>
   instead.
  </para>

  <table>
   <title><structname>pg_user_mapping</structname> Columns</title>
   <tgroup cols="1">
    <thead>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       Column Type
      </para>
      <para>
       Description
      </para></entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>oid</structfield> <type>oid</type>
      </para>
      <para>
       Row identifier
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>umuser</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       OID of the local role being mapped, or zero if the user mapping is public
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>umserver</structfield> <type>oid</type>
       (references <link linkend="catalog-pg-foreign-server"><structname>pg_foreign_server</structname></link>.<structfield>oid</structfield>)
      </para>
      <para>
       The OID of the foreign server that contains this mapping
      </para></entry>
     </row>

     <row>
      <entry role="catalog_table_entry"><para role="column_definition">
       <structfield>umoptions</structfield> <type>text[]</type>
      </para>
      <para>
       User mapping specific options, as <quote>keyword=value</quote> strings
      </para></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

</chapter>
