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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 V1.79.1" /><link rel="prev" href="functions-trigger.html" title="9.27. Trigger Functions" /><link rel="next" href="functions-statistics.html" title="9.29. Statistics Information Functions" /></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 12.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="functions-statistics.html" title="9.29. Statistics Information Functions">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 39. Event Triggers">Chapter 39</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 9.96. Table Rewrite Information">Table 9.96</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 9.96. 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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