<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Event Trigger Functions</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REV="MADE" HREF="mailto:pgsql-docs@postgresql.org"><LINK REL="HOME" TITLE="PostgreSQL 9.6.17 Documentation" HREF="index.html"><LINK REL="UP" TITLE="Functions and Operators" HREF="functions.html"><LINK REL="PREVIOUS" TITLE="Trigger Functions" HREF="functions-trigger.html"><LINK REL="NEXT" TITLE="Type Conversion" HREF="typeconv.html"><LINK REL="STYLESHEET" TYPE="text/css" HREF="stylesheet.css"><META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"><META NAME="creation" CONTENT="2020-02-15T12:30:38"></HEAD ><BODY CLASS="SECT1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="4" ALIGN="center" VALIGN="bottom" ><A HREF="index.html" >PostgreSQL 9.6.17 Documentation</A ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A TITLE="Trigger Functions" HREF="functions-trigger.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="10%" ALIGN="left" VALIGN="top" ><A HREF="functions.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="60%" ALIGN="center" VALIGN="bottom" >Chapter 9. Functions and Operators</TD ><TD WIDTH="20%" ALIGN="right" VALIGN="top" ><A TITLE="Type Conversion" HREF="typeconv.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="FUNCTIONS-EVENT-TRIGGERS" >9.28. Event Trigger Functions</A ></H1 ><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 HREF="event-triggers.html" >Chapter 38</A >. </P ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PG-EVENT-TRIGGER-DDL-COMMAND-END-FUNCTIONS" >9.28.1. Capturing Changes at Command End</A ></H2 ><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 <TT CLASS="LITERAL" >ddl_command_end</TT > 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: <DIV CLASS="INFORMALTABLE" ><P ></P ><A NAME="AEN25055" ></A ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><THEAD ><TR ><TH >Name</TH ><TH >Type</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="LITERAL" >classid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD >OID of catalog the object belongs in</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >objid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD >OID of the object itself</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >objsubid</TT ></TD ><TD ><TT CLASS="TYPE" >integer</TT ></TD ><TD >Sub-object ID (e.g. attribute number for a column)</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >command_tag</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD >Command tag</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >object_type</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD >Type of the object</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >schema_name</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD > Name of the schema the object belongs in, if any; otherwise <TT CLASS="LITERAL" >NULL</TT >. No quoting is applied. </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >object_identity</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD > Text rendering of the object identity, schema-qualified. Each identifier included in the identity is quoted if necessary. </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >in_extension</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD >True if the command is part of an extension script</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >command</TT ></TD ><TD ><TT CLASS="TYPE" >pg_ddl_command</TT ></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 ><P ></P ></DIV > </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PG-EVENT-TRIGGER-SQL-DROP-FUNCTIONS" >9.28.2. Processing Objects Dropped by a DDL Command</A ></H2 ><P > <CODE CLASS="FUNCTION" >pg_event_trigger_dropped_objects</CODE > returns a list of all objects dropped by the command in whose <TT CLASS="LITERAL" >sql_drop</TT > 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: <DIV CLASS="INFORMALTABLE" ><P ></P ><A NAME="AEN25127" ></A ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><THEAD ><TR ><TH >Name</TH ><TH >Type</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD ><TT CLASS="LITERAL" >classid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD >OID of catalog the object belonged in</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >objid</TT ></TD ><TD ><TT CLASS="TYPE" >oid</TT ></TD ><TD >OID of the object itself</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >objsubid</TT ></TD ><TD ><TT CLASS="TYPE" >integer</TT ></TD ><TD >Sub-object ID (e.g. attribute number for a column)</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >original</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD >True if this was one of the root object(s) of the deletion</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >normal</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD > True if there was a normal dependency relationship in the dependency graph leading to this object </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >is_temporary</TT ></TD ><TD ><TT CLASS="TYPE" >bool</TT ></TD ><TD > True if this was a temporary object </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >object_type</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD >Type of the object</TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >schema_name</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD > Name of the schema the object belonged in, if any; otherwise <TT CLASS="LITERAL" >NULL</TT >. No quoting is applied. </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >object_name</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD > Name of the object, if the combination of schema and name can be used as a unique identifier for the object; otherwise <TT CLASS="LITERAL" >NULL</TT >. No quoting is applied, and name is never schema-qualified. </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >object_identity</TT ></TD ><TD ><TT CLASS="TYPE" >text</TT ></TD ><TD > Text rendering of the object identity, schema-qualified. Each identifier included in the identity is quoted if necessary. </TD ></TR ><TR ><TD ><TT CLASS="LITERAL" >address_names</TT ></TD ><TD ><TT CLASS="TYPE" >text[]</TT ></TD ><TD > An array that, together with <TT CLASS="LITERAL" >object_type</TT > and <TT CLASS="LITERAL" >address_args</TT >, 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 ><TT CLASS="LITERAL" >address_args</TT ></TD ><TD ><TT CLASS="TYPE" >text[]</TT ></TD ><TD > Complement for <TT CLASS="LITERAL" >address_names</TT > </TD ></TR ></TBODY ></TABLE ><P ></P ></DIV > </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 PROCEDURE test_event_trigger_for_drops();</PRE ><P> </P ></DIV ><DIV CLASS="SECT2" ><H2 CLASS="SECT2" ><A NAME="PG-EVENT-TRIGGER-TABLE-REWRITE-FUNCTIONS" >9.28.3. Handling a Table Rewrite Event</A ></H2 ><P > The functions shown in <A HREF="functions-event-triggers.html#FUNCTIONS-EVENT-TRIGGER-TABLE-REWRITE" >Table 9-88</A > provide information about a table for which a <TT CLASS="LITERAL" >table_rewrite</TT > event has just been called. If called in any other context, an error is raised. </P ><DIV CLASS="TABLE" ><A NAME="FUNCTIONS-EVENT-TRIGGER-TABLE-REWRITE" ></A ><P ><B >Table 9-88. Table Rewrite information</B ></P ><TABLE BORDER="1" CLASS="CALSTABLE" ><COL><COL><COL><THEAD ><TR ><TH >Name</TH ><TH >Return Type</TH ><TH >Description</TH ></TR ></THEAD ><TBODY ><TR ><TD > <TT CLASS="LITERAL" ><CODE CLASS="FUNCTION" >pg_event_trigger_table_rewrite_oid()</CODE ></TT > </TD ><TD ><TT CLASS="TYPE" >Oid</TT ></TD ><TD >The OID of the table about to be rewritten.</TD ></TR ><TR ><TD > <TT CLASS="LITERAL" ><CODE CLASS="FUNCTION" >pg_event_trigger_table_rewrite_reason()</CODE ></TT > </TD ><TD ><TT CLASS="TYPE" >int</TT ></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 ><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 PROCEDURE test_event_trigger_table_rewrite_oid();</PRE ><P> </P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="functions-trigger.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="typeconv.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Trigger Functions</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="functions.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Type Conversion</TD ></TR ></TABLE ></DIV ></BODY ></HTML >