</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>

<entry><link linkend="catalog-pg-collation"><structname>pg_collation</structname></link></entry>

<entry>collations (locale information)</entry>

</row>

<row>

<entry><link linkend="catalog-pg-collation"><structname>pg_collation</structname></link></entry>

<entry>collations (locale information)</entry>

<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>

</para>

</sect1>

<sect1 id="catalog-pg-event-trigger">

<title><structname>pg_event_trigger</structname></title>

<sect1 id="catalog-pg-collation">

<title><structname>pg_collation</structname></title>

<indexterm zone="catalog-pg-event-trigger">

<primary>pg_event_trigger</primary>

<indexterm zone="catalog-pg-collation">

<primary>pg_collation</primary>

</indexterm>

<para>

The catalog <structname>pg_event_trigger</structname> stores event triggers.

See <xref linkend="event-triggers"> for more information.

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_event_trigger</> Columns</title>

<title><structname>pg_collation</> Columns</title>

<tgroup cols="4">

<thead>

<tbody>

<row>

<entry><structfield>evtname</structfield></entry>

<entry><type>name</type></entry>

<entry><structfield>oid</structfield></entry>

<entry><type>oid</type></entry>

<entry></entry>

<entry>Trigger name (must beunique)</entry>

<entry>Row identifier (hidden attribute;must beexplicitly selected)</entry>

</row>

<row>

<entry><structfield>evtevent</structfield></entry>

<entry><structfield>collname</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry>Identifies the event for which this trigger fires</entry>

<entry>Collation name (unique per namespace and encoding)</entry>

</row>

<row>

<entry><structfield>evtowner</structfield></entry>

<entry><structfield>collnamespace</structfield></entry>

<entry><type>oid</type></entry>

<entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>

<entry>Owner of the event trigger</entry>

<entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>

<entry>

The OID of the namespace that contains this collation

</entry>

</row>

<row>

<entry><structfield>evtfoid</structfield></entry>

<entry><structfield>collowner</structfield></entry>

<entry><type>oid</type></entry>

<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>

<entry>The function to be called</entry>

<entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>

<entry>Owner of the collation</entry>

</row>

<row>

<entry><structfield>evtenabled</structfield></entry>

<entry><type>char</type></entry>

<entry><structfield>collencoding</structfield></entry>

<entry><type>int4</type></entry>

<entry></entry>

<entry>

Controls in which <xref linkend="guc-session-replication-role"> modes

the event trigger fires.

<literal>O</> = trigger fires in <quote>origin</> and <quote>local</> modes,

<literal>D</> = trigger is disabled,

<literal>R</> = trigger fires in <quote>replica</> mode,

<literal>A</> = trigger fires always.

</entry>

<entry>Encoding in which the collation is applicable, or -1 if it

works for any encoding</entry>

</row>

<row>

<entry><structfield>evttags</structfield></entry>

<entry><type>text[]</type></entry>

<entry><structfield>collcollate</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry>

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.

</entry>

<entry><symbol>LC_COLLATE</> for this collation object</entry>

</row>

<row>

<entry><structfield>collctype</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry><symbol>LC_CTYPE</> for this collation object</entry>

</row>

</tbody>

</tgroup>

</table>

<para>

Note that the unique key on this catalog is (<structfield>collname</>,

<structfield>collencoding</>, <structfield>collnamespace</>) not just

(<structfield>collname</>, <structfield>collnamespace</>).

<productname>PostgreSQL</productname> generally ignores all

collations that do not have <structfield>collencoding</> 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</> = -1

is forbidden. Therefore it is sufficient to use a qualified SQL name

(<replaceable>schema</>.<replaceable>name</>) 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</> 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</> 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</>. This would currently have to be done manually.

</para>

</sect1>

<sect1 id="catalog-pg-constraint">

relation.

</para>

</note>

</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</> Columns</title>

<tgroup cols="4">

<thead>

<row>

<entry>Name</entry>

<entry>Type</entry>

<entry>References</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><structfield>oid</structfield></entry>

<entry><type>oid</type></entry>

<entry></entry>

<entry>Row identifier (hidden attribute; must be explicitly selected)</entry>

</row>

<row>

<entry><structfield>collname</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry>Collation name (unique per namespace and encoding)</entry>

</row>

<row>

<entry><structfield>collnamespace</structfield></entry>

<entry><type>oid</type></entry>

<entry><literal><link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.oid</literal></entry>

<entry>

The OID of the namespace that contains this collation

</entry>

</row>

<row>

<entry><structfield>collowner</structfield></entry>

<entry><type>oid</type></entry>

<entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>

<entry>Owner of the collation</entry>

</row>

<row>

<entry><structfield>collencoding</structfield></entry>

<entry><type>int4</type></entry>

<entry></entry>

<entry>Encoding in which the collation is applicable, or -1 if it

works for any encoding</entry>

</row>

<row>

<entry><structfield>collcollate</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry><symbol>LC_COLLATE</> for this collation object</entry>

</row>

<row>

<entry><structfield>collctype</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry><symbol>LC_CTYPE</> for this collation object</entry>

</row>

</tbody>

</tgroup>

</table>

<para>

Note that the unique key on this catalog is (<structfield>collname</>,

<structfield>collencoding</>, <structfield>collnamespace</>) not just

(<structfield>collname</>, <structfield>collnamespace</>).

<productname>PostgreSQL</productname> generally ignores all

collations that do not have <structfield>collencoding</> 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</> = -1

is forbidden. Therefore it is sufficient to use a qualified SQL name

(<replaceable>schema</>.<replaceable>name</>) 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</> 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</> 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</>. This would currently have to be done manually.

</para>

</sect1>

<sect1 id="catalog-pg-conversion">

<title><structname>pg_conversion</structname></title>

</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</> Columns</title>

<tgroup cols="4">

<thead>

<row>

<entry>Name</entry>

<entry>Type</entry>

<entry>References</entry>

<entry>Description</entry>

</row>

</thead>

<tbody>

<row>

<entry><structfield>evtname</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry>Trigger name (must be unique)</entry>

</row>

<row>

<entry><structfield>evtevent</structfield></entry>

<entry><type>name</type></entry>

<entry></entry>

<entry>Identifies the event for which this trigger fires</entry>

</row>

<row>

<entry><structfield>evtowner</structfield></entry>

<entry><type>oid</type></entry>

<entry><literal><link linkend="catalog-pg-authid"><structname>pg_authid</structname></link>.oid</literal></entry>

<entry>Owner of the event trigger</entry>

</row>

<row>

<entry><structfield>evtfoid</structfield></entry>

<entry><type>oid</type></entry>

<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>

<entry>The function to be called</entry>

</row>

<row>

<entry><structfield>evtenabled</structfield></entry>

<entry><type>char</type></entry>

<entry></entry>

<entry>

Controls in which <xref linkend="guc-session-replication-role"> modes

the event trigger fires.

<literal>O</> = trigger fires in <quote>origin</> and <quote>local</> modes,

<literal>D</> = trigger is disabled,

<literal>R</> = trigger fires in <quote>replica</> mode,

<literal>A</> = trigger fires always.

</entry>

</row>

<row>

<entry><structfield>evttags</structfield></entry>

<entry><type>text[]</type></entry>

<entry></entry>

<entry>

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.

</entry>

</row>

</tbody>

</tgroup>

</table>

</sect1>

<sect1 id="catalog-pg-extension">

<title><structname>pg_extension</structname></title>