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+<!--
+doc/src/sgml/ref/create_event_trigger.sgml
+PostgreSQL documentation
+-->
+
+<refentry id="sql-createeventtrigger">
+ <indexterm zone="sql-createeventtrigger">
+  <primary>CREATE EVENT TRIGGER</primary>
+ </indexterm>
+
+ <refmeta>
+  <refentrytitle>CREATE EVENT TRIGGER</refentrytitle>
+  <manvolnum>7</manvolnum>
+  <refmiscinfo>SQL - Language Statements</refmiscinfo>
+ </refmeta>
+
+ <refnamediv>
+  <refname>CREATE EVENT TRIGGER</refname>
+  <refpurpose>define a new event trigger</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+<synopsis>
+CREATE EVENT TRIGGER <replaceable class="parameter">name</replaceable>
+    ON <replaceable class="parameter">event</replaceable>
+    [ WHEN <replaceable class="parameter">filter_variable</replaceable> IN (<replaceable class="parameter">filter_value</replaceable> [, ... ]) [ AND ... ] ]
+    EXECUTE { FUNCTION | PROCEDURE } <replaceable class="parameter">function_name</replaceable>()
+</synopsis>
+ </refsynopsisdiv>
+
+ <refsect1>
+  <title>Description</title>
+
+  <para>
+   <command>CREATE EVENT TRIGGER</command> creates a new event trigger.
+   Whenever the designated event occurs and the <literal>WHEN</literal> condition
+   associated with the trigger, if any, is satisfied, the trigger function
+   will be executed.  For a general introduction to event triggers, see
+   <xref linkend="event-triggers"/>.  The user who creates an event trigger
+   becomes its owner.
+  </para>
+ </refsect1>
+
+ <refsect1>
+  <title>Parameters</title>
+
+  <variablelist>
+   <varlistentry>
+    <term><replaceable class="parameter">name</replaceable></term>
+    <listitem>
+     <para>
+      The name to give the new trigger.  This name must be unique within
+      the database.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">event</replaceable></term>
+    <listitem>
+     <para>
+      The name of the event that triggers a call to the given function.
+      See <xref linkend="event-trigger-definition"/> for more information
+      on event names.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">filter_variable</replaceable></term>
+    <listitem>
+     <para>
+      The name of a variable used to filter events.  This makes it possible
+      to restrict the firing of the trigger to a subset of the cases in which
+      it is supported.  Currently the only supported
+      <replaceable class="parameter">filter_variable</replaceable>
+      is <literal>TAG</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">filter_value</replaceable></term>
+    <listitem>
+     <para>
+      A list of values for the
+      associated <replaceable class="parameter">filter_variable</replaceable>
+      for which the trigger should fire.  For <literal>TAG</literal>, this means a
+      list of command tags (e.g., <literal>'DROP FUNCTION'</literal>).
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
+    <term><replaceable class="parameter">function_name</replaceable></term>
+    <listitem>
+     <para>
+      A user-supplied function that is declared as taking no argument and
+      returning type <literal>event_trigger</literal>.
+     </para>
+
+     <para>
+      In the syntax of <literal>CREATE EVENT TRIGGER</literal>, the keywords
+      <literal>FUNCTION</literal> and <literal>PROCEDURE</literal> are
+      equivalent, but the referenced function must in any case be a function,
+      not a procedure.  The use of the keyword <literal>PROCEDURE</literal>
+      here is historical and deprecated.
+     </para>
+    </listitem>
+   </varlistentry>
+
+  </variablelist>
+ </refsect1>
+
+ <refsect1 id="sql-createeventtrigger-notes">
+  <title>Notes</title>
+
+  <para>
+   Only superusers can create event triggers.
+  </para>
+
+  <para>
+   Event triggers are disabled in single-user mode (see <xref
+   linkend="app-postgres"/>).  If an erroneous event trigger disables the
+   database so much that you can't even drop the trigger, restart in
+   single-user mode and you'll be able to do that.
+  </para>
+ </refsect1>
+
+ <refsect1 id="sql-createeventtrigger-examples">
+  <title>Examples</title>
+
+  <para>
+   Forbid the execution of any <link linkend="ddl">DDL</link> command:
+
+<programlisting>
+CREATE OR REPLACE FUNCTION abort_any_command()
+  RETURNS event_trigger
+ LANGUAGE plpgsql
+  AS $$
+BEGIN
+  RAISE EXCEPTION 'command % is disabled', tg_tag;
+END;
+$$;
+
+CREATE EVENT TRIGGER abort_ddl ON ddl_command_start
+   EXECUTE FUNCTION abort_any_command();
+</programlisting></para>
+ </refsect1>
+
+ <refsect1 id="sql-createeventtrigger-compatibility">
+  <title>Compatibility</title>
+
+  <para>
+   There is no <command>CREATE EVENT TRIGGER</command> statement in the
+   SQL standard.
+  </para>
+
+ </refsect1>
+
+ <refsect1>
+  <title>See Also</title>
+
+  <simplelist type="inline">
+   <member><xref linkend="sql-altereventtrigger"/></member>
+   <member><xref linkend="sql-dropeventtrigger"/></member>
+   <member><xref linkend="sql-createfunction"/></member>
+  </simplelist>
+ </refsect1>
+</refentry>