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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>9.28. Event Trigger Functions</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 Vsnapshot" /><link rel="prev" href="functions-trigger.html" title="9.27. Trigger Functions" /><link rel="next" href="typeconv.html" title="Chapter 10. Type Conversion" /></head><body><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">9.28. Event Trigger Functions</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="functions-trigger.html" title="9.27. Trigger Functions">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="functions.html" title="Chapter 9. Functions and Operators">Up</a></td><th width="60%" align="center">Chapter 9. Functions and Operators</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 11.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="typeconv.html" title="Chapter 10. Type Conversion">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="FUNCTIONS-EVENT-TRIGGERS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">9.28. Event Trigger Functions</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="functions-event-triggers.html#PG-EVENT-TRIGGER-DDL-COMMAND-END-FUNCTIONS">9.28.1. Capturing Changes at Command End</a></span></dt><dt><span class="sect2"><a href="functions-event-triggers.html#PG-EVENT-TRIGGER-SQL-DROP-FUNCTIONS">9.28.2. Processing Objects Dropped by a DDL Command</a></span></dt><dt><span class="sect2"><a href="functions-event-triggers.html#PG-EVENT-TRIGGER-TABLE-REWRITE-FUNCTIONS">9.28.3. Handling a Table Rewrite Event</a></span></dt></dl></div><p>
<span class="productname">PostgreSQL</span> provides these helper functions
to retrieve information from event triggers.
</p><p>
For more information about event triggers,
see <a class="xref" href="event-triggers.html" title="Chapter 40. Event Triggers">Chapter 40</a>.
</p><div class="sect2" id="PG-EVENT-TRIGGER-DDL-COMMAND-END-FUNCTIONS"><div class="titlepage"><div><div><h3 class="title">9.28.1. Capturing Changes at Command End</h3></div></div></div><a id="id-1.5.8.33.4.2" class="indexterm"></a><p>
<code class="function">pg_event_trigger_ddl_commands</code> returns a list of
<acronym class="acronym">DDL</acronym> commands executed by each user action,
when invoked in a function attached to a
<code class="literal">ddl_command_end</code> event trigger. If called in any other
context, an error is raised.
<code class="function">pg_event_trigger_ddl_commands</code> returns one row for each
base command executed; some commands that are a single SQL sentence
may return more than one row. This function returns the following
columns:
</p><div class="informaltable"><table class="informaltable" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Type</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">classid</code></td><td><code class="type">oid</code></td><td>OID of catalog the object belongs in</td></tr><tr><td><code class="literal">objid</code></td><td><code class="type">oid</code></td><td>OID of the object itself</td></tr><tr><td><code class="literal">objsubid</code></td><td><code class="type">integer</code></td><td>Sub-object ID (e.g. attribute number for a column)</td></tr><tr><td><code class="literal">command_tag</code></td><td><code class="type">text</code></td><td>Command tag</td></tr><tr><td><code class="literal">object_type</code></td><td><code class="type">text</code></td><td>Type of the object</td></tr><tr><td><code class="literal">schema_name</code></td><td><code class="type">text</code></td><td>
Name of the schema the object belongs in, if any; otherwise <code class="literal">NULL</code>.
No quoting is applied.
</td></tr><tr><td><code class="literal">object_identity</code></td><td><code class="type">text</code></td><td>
Text rendering of the object identity, schema-qualified. Each
identifier included in the identity is quoted if necessary.
</td></tr><tr><td><code class="literal">in_extension</code></td><td><code class="type">bool</code></td><td>True if the command is part of an extension script</td></tr><tr><td><code class="literal">command</code></td><td><code class="type">pg_ddl_command</code></td><td>
A complete representation of the command, in internal format.
This cannot be output directly, but it can be passed to other
functions to obtain different pieces of information about the
command.
</td></tr></tbody></table></div><p>
</p></div><div class="sect2" id="PG-EVENT-TRIGGER-SQL-DROP-FUNCTIONS"><div class="titlepage"><div><div><h3 class="title">9.28.2. Processing Objects Dropped by a DDL Command</h3></div></div></div><a id="id-1.5.8.33.5.2" class="indexterm"></a><p>
<code class="function">pg_event_trigger_dropped_objects</code> returns a list of all objects
dropped by the command in whose <code class="literal">sql_drop</code> event it is called.
If called in any other context,
<code class="function">pg_event_trigger_dropped_objects</code> raises an error.
<code class="function">pg_event_trigger_dropped_objects</code> returns the following columns:
</p><div class="informaltable"><table class="informaltable" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Type</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">classid</code></td><td><code class="type">oid</code></td><td>OID of catalog the object belonged in</td></tr><tr><td><code class="literal">objid</code></td><td><code class="type">oid</code></td><td>OID of the object itself</td></tr><tr><td><code class="literal">objsubid</code></td><td><code class="type">integer</code></td><td>Sub-object ID (e.g. attribute number for a column)</td></tr><tr><td><code class="literal">original</code></td><td><code class="type">bool</code></td><td>True if this was one of the root object(s) of the deletion</td></tr><tr><td><code class="literal">normal</code></td><td><code class="type">bool</code></td><td>
True if there was a normal dependency relationship
in the dependency graph leading to this object
</td></tr><tr><td><code class="literal">is_temporary</code></td><td><code class="type">bool</code></td><td>
True if this was a temporary object
</td></tr><tr><td><code class="literal">object_type</code></td><td><code class="type">text</code></td><td>Type of the object</td></tr><tr><td><code class="literal">schema_name</code></td><td><code class="type">text</code></td><td>
Name of the schema the object belonged in, if any; otherwise <code class="literal">NULL</code>.
No quoting is applied.
</td></tr><tr><td><code class="literal">object_name</code></td><td><code class="type">text</code></td><td>
Name of the object, if the combination of schema and name can be
used as a unique identifier for the object; otherwise <code class="literal">NULL</code>.
No quoting is applied, and name is never schema-qualified.
</td></tr><tr><td><code class="literal">object_identity</code></td><td><code class="type">text</code></td><td>
Text rendering of the object identity, schema-qualified. Each
identifier included in the identity is quoted if necessary.
</td></tr><tr><td><code class="literal">address_names</code></td><td><code class="type">text[]</code></td><td>
An array that, together with <code class="literal">object_type</code> and
<code class="literal">address_args</code>, can be used by
the <code class="function">pg_get_object_address()</code> function to
recreate the object address in a remote server containing an
identically named object of the same kind
</td></tr><tr><td><code class="literal">address_args</code></td><td><code class="type">text[]</code></td><td>
Complement for <code class="literal">address_names</code>
</td></tr></tbody></table></div><p>
</p><p>
The <code class="function">pg_event_trigger_dropped_objects</code> function can be used
in an event trigger like this:
</p><pre class="programlisting">
CREATE FUNCTION test_event_trigger_for_drops()
RETURNS event_trigger LANGUAGE plpgsql AS $$
DECLARE
obj record;
BEGIN
FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects()
LOOP
RAISE NOTICE '% dropped object: % %.% %',
tg_tag,
obj.object_type,
obj.schema_name,
obj.object_name,
obj.object_identity;
END LOOP;
END
$$;
CREATE EVENT TRIGGER test_event_trigger_for_drops
ON sql_drop
EXECUTE FUNCTION test_event_trigger_for_drops();
</pre><p>
</p></div><div class="sect2" id="PG-EVENT-TRIGGER-TABLE-REWRITE-FUNCTIONS"><div class="titlepage"><div><div><h3 class="title">9.28.3. Handling a Table Rewrite Event</h3></div></div></div><p>
The functions shown in
<a class="xref" href="functions-event-triggers.html#FUNCTIONS-EVENT-TRIGGER-TABLE-REWRITE" title="Table 9.90. Table Rewrite information">Table 9.90</a>
provide information about a table for which a
<code class="literal">table_rewrite</code> event has just been called.
If called in any other context, an error is raised.
</p><div class="table" id="FUNCTIONS-EVENT-TRIGGER-TABLE-REWRITE"><p class="title"><strong>Table 9.90. Table Rewrite information</strong></p><div class="table-contents"><table class="table" summary="Table Rewrite information" border="1"><colgroup><col /><col /><col /></colgroup><thead><tr><th>Name</th><th>Return Type</th><th>Description</th></tr></thead><tbody><tr><td>
<a id="id-1.5.8.33.6.3.2.2.1.1.1" class="indexterm"></a>
<code class="literal"><code class="function">pg_event_trigger_table_rewrite_oid()</code></code>
</td><td><code class="type">Oid</code></td><td>The OID of the table about to be rewritten.</td></tr><tr><td>
<a id="id-1.5.8.33.6.3.2.2.2.1.1" class="indexterm"></a>
<code class="literal"><code class="function">pg_event_trigger_table_rewrite_reason()</code></code>
</td><td><code class="type">int</code></td><td>
The reason code(s) explaining the reason for rewriting. The exact
meaning of the codes is release dependent.
</td></tr></tbody></table></div></div><br class="table-break" /><p>
The <code class="function">pg_event_trigger_table_rewrite_oid</code> function can be used
in an event trigger like this:
</p><pre class="programlisting">
CREATE FUNCTION test_event_trigger_table_rewrite_oid()
RETURNS event_trigger
LANGUAGE plpgsql AS
$$
BEGIN
RAISE NOTICE 'rewriting table % for reason %',
pg_event_trigger_table_rewrite_oid()::regclass,
pg_event_trigger_table_rewrite_reason();
END;
$$;
CREATE EVENT TRIGGER test_table_rewrite_oid
ON table_rewrite
EXECUTE FUNCTION test_event_trigger_table_rewrite_oid();
</pre><p>
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