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><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="AEN25114"
></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="AEN25186"
></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>
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