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><H1
><A
NAME="SQL-CREATEEVENTTRIGGER"
></A
>CREATE EVENT TRIGGER</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN70197"
></A
><H2
>Name</H2
>CREATE EVENT TRIGGER -- define a new event trigger</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN70202"
></A
><H2
>Synopsis</H2
><PRE
CLASS="SYNOPSIS"
>CREATE EVENT TRIGGER <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>
ON <TT
CLASS="REPLACEABLE"
><I
>event</I
></TT
>
[ WHEN <TT
CLASS="REPLACEABLE"
><I
>filter_variable</I
></TT
> IN (filter_value [, ... ]) [ AND ... ] ]
EXECUTE PROCEDURE <TT
CLASS="REPLACEABLE"
><I
>function_name</I
></TT
>()</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN70208"
></A
><H2
>Description</H2
><P
> <TT
CLASS="COMMAND"
>CREATE EVENT TRIGGER</TT
> creates a new event trigger.
Whenever the designated event occurs and the <TT
CLASS="LITERAL"
>WHEN</TT
> condition
associated with the trigger, if any, is satisfied, the trigger function
will be executed. For a general introduction to event triggers, see
<A
HREF="event-triggers.html"
>Chapter 37</A
>. The user who creates an event trigger
becomes its owner.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN70214"
></A
><H2
>Parameters</H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></DT
><DD
><P
> The name to give the new trigger. This name must be unique within
the database.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>event</I
></TT
></DT
><DD
><P
> The name of the event that triggers a call to the given function.
See <A
HREF="event-trigger-definition.html"
>Section 37.1</A
> for more information
on event names.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>filter_variable</I
></TT
></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
<TT
CLASS="REPLACEABLE"
><I
>filter_variable</I
></TT
>
is <TT
CLASS="LITERAL"
>TAG</TT
>.
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>filter_value</I
></TT
></DT
><DD
><P
> A list of values for the
associated <TT
CLASS="REPLACEABLE"
><I
>filter_variable</I
></TT
>
for which the trigger should fire. For <TT
CLASS="LITERAL"
>TAG</TT
>, this means a
list of command tags (e.g. <TT
CLASS="LITERAL"
>'DROP FUNCTION'</TT
>).
</P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>function_name</I
></TT
></DT
><DD
><P
> A user-supplied function that is declared as taking no argument and
returning type <TT
CLASS="LITERAL"
>event_trigger</TT
>.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="SQL-CREATEEVENTTRIGGER-NOTES"
></A
><H2
>Notes</H2
><P
> Only superusers can create event triggers.
</P
><P
> Event triggers are disabled in single-user mode (see <A
HREF="app-postgres.html"
><SPAN
CLASS="APPLICATION"
>postgres</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"
><A
NAME="SQL-CREATEEVENTTRIGGER-EXAMPLES"
></A
><H2
>Examples</H2
><P
> Forbid the execution of any <A
HREF="ddl.html"
>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 PROCEDURE abort_any_command();</PRE
><P></P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="SQL-CREATEEVENTTRIGGER-COMPATIBILITY"
></A
><H2
>Compatibility</H2
><P
> There is no <TT
CLASS="COMMAND"
>CREATE EVENT TRIGGER</TT
> statement in the
SQL standard.
</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN70263"
></A
><H2
>See Also</H2
><A
HREF="sql-altereventtrigger.html"
>ALTER EVENT TRIGGER</A
>, <A
HREF="sql-dropeventtrigger.html"
>DROP EVENT TRIGGER</A
>, <A
HREF="sql-createfunction.html"
>CREATE FUNCTION</A
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