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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>CREATE EVENT TRIGGER</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets V1.79.1" /><link rel="prev" href="sql-createdomain.html" title="CREATE DOMAIN" /><link rel="next" href="sql-createextension.html" title="CREATE EXTENSION" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">CREATE EVENT TRIGGER</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="sql-createdomain.html" title="CREATE DOMAIN">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><th width="60%" align="center">SQL Commands</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="sql-createextension.html" title="CREATE EXTENSION">Next</a></td></tr></table><hr></hr></div><div class="refentry" id="SQL-CREATEEVENTTRIGGER"><div class="titlepage"></div><a id="id-1.9.3.63.1" class="indexterm"></a><div class="refnamediv"><h2><span class="refentrytitle">CREATE EVENT TRIGGER</span></h2><p>CREATE EVENT TRIGGER — define a new event trigger</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><pre class="synopsis">
CREATE EVENT TRIGGER <em class="replaceable"><code>name</code></em>
ON <em class="replaceable"><code>event</code></em>
[ WHEN <em class="replaceable"><code>filter_variable</code></em> IN (filter_value [, ... ]) [ AND ... ] ]
EXECUTE { FUNCTION | PROCEDURE } <em class="replaceable"><code>function_name</code></em>()
</pre></div><div class="refsect1" id="id-1.9.3.63.5"><h2>Description</h2><p>
<code class="command">CREATE EVENT TRIGGER</code> creates a new event trigger.
Whenever the designated event occurs and the <code class="literal">WHEN</code> condition
associated with the trigger, if any, is satisfied, the trigger function
will be executed. For a general introduction to event triggers, see
<a class="xref" href="event-triggers.html" title="Chapter 39. Event Triggers">Chapter 39</a>. The user who creates an event trigger
becomes its owner.
</p></div><div class="refsect1" id="id-1.9.3.63.6"><h2>Parameters</h2><div class="variablelist"><dl class="variablelist"><dt><span class="term"><em class="replaceable"><code>name</code></em></span></dt><dd><p>
The name to give the new trigger. This name must be unique within
the database.
</p></dd><dt><span class="term"><em class="replaceable"><code>event</code></em></span></dt><dd><p>
The name of the event that triggers a call to the given function.
See <a class="xref" href="event-trigger-definition.html" title="39.1. Overview of Event Trigger Behavior">Section 39.1</a> for more information
on event names.
</p></dd><dt><span class="term"><em class="replaceable"><code>filter_variable</code></em></span></dt><dd><p>
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
<em class="replaceable"><code>filter_variable</code></em>
is <code class="literal">TAG</code>.
</p></dd><dt><span class="term"><em class="replaceable"><code>filter_value</code></em></span></dt><dd><p>
A list of values for the
associated <em class="replaceable"><code>filter_variable</code></em>
for which the trigger should fire. For <code class="literal">TAG</code>, this means a
list of command tags (e.g., <code class="literal">'DROP FUNCTION'</code>).
</p></dd><dt><span class="term"><em class="replaceable"><code>function_name</code></em></span></dt><dd><p>
A user-supplied function that is declared as taking no argument and
returning type <code class="literal">event_trigger</code>.
</p><p>
In the syntax of <code class="literal">CREATE EVENT TRIGGER</code>, the keywords
<code class="literal">FUNCTION</code> and <code class="literal">PROCEDURE</code> are
equivalent, but the referenced function must in any case be a function,
not a procedure. The use of the keyword <code class="literal">PROCEDURE</code>
here is historical and deprecated.
</p></dd></dl></div></div><div class="refsect1" id="SQL-CREATEEVENTTRIGGER-NOTES"><h2>Notes</h2><p>
Only superusers can create event triggers.
</p><p>
Event triggers are disabled in single-user mode (see <a class="xref" href="app-postgres.html" title="postgres"><span class="refentrytitle"><span class="application">postgres</span></span></a>). 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.
</p></div><div class="refsect1" id="SQL-CREATEEVENTTRIGGER-EXAMPLES"><h2>Examples</h2><p>
Forbid the execution of any <a class="link" href="ddl.html" title="Chapter 5. Data Definition">DDL</a> command:
</p><pre class="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();
</pre></div><div class="refsect1" id="SQL-CREATEEVENTTRIGGER-COMPATIBILITY"><h2>Compatibility</h2><p>
There is no <code class="command">CREATE EVENT TRIGGER</code> statement in the
SQL standard.
</p></div><div class="refsect1" id="id-1.9.3.63.10"><h2>See Also</h2><span class="simplelist"><a class="xref" href="sql-altereventtrigger.html" title="ALTER EVENT TRIGGER"><span class="refentrytitle">ALTER EVENT TRIGGER</span></a>, <a class="xref" href="sql-dropeventtrigger.html" title="DROP EVENT TRIGGER"><span class="refentrytitle">DROP EVENT TRIGGER</span></a>, <a class="xref" href="sql-createfunction.html" title="CREATE FUNCTION"><span class="refentrytitle">CREATE FUNCTION</span></a></span></div></div><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="sql-createdomain.html" title="CREATE DOMAIN">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="sql-commands.html" title="SQL Commands">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="sql-createextension.html" title="CREATE EXTENSION">Next</a></td></tr><tr><td width="40%" align="left" valign="top">CREATE DOMAIN </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 13.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> CREATE EXTENSION</td></tr></table></div></body></html>
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