create_event_trigger(7)

NAME#

CREATE_EVENT_TRIGGER - define a new event trigger

SYNOPSIS#

CREATE EVENT TRIGGER \nname\n
\n
    ON \nevent\n
\n
    [ WHEN \nfilter_variable\n IN (\nfilter_value\n [, ... ]) [ AND ... ] ]
\n
    EXECUTE { FUNCTION | PROCEDURE } \nfunction_name\n()

DESCRIPTION#

CREATE EVENT TRIGGER creates a new event trigger. Whenever the designated event occurs and the WHEN condition associated with the trigger, if any, is satisfied, the trigger function will be executed. For a general introduction to event triggers, see Chapter 38. The user who creates an event trigger becomes its owner.

PARAMETERS#

name

event

filter_variable

filter_value

function_name

In the syntax of CREATE EVENT TRIGGER, the keywords FUNCTION and PROCEDURE are equivalent, but the referenced function must in any case be a function, not a procedure. The use of the keyword PROCEDURE here is historical and deprecated.

NOTES#

Only superusers can create event triggers.

Event triggers are disabled in single-user mode (see postgres(1)) as well as when event_triggers is set to false. If an erroneous event trigger disables the database so much that you can't even drop the trigger, restart with event_triggers set to false to temporarily disable event triggers, or in single-user mode, and you'll be able to do that.

EXAMPLES#

Forbid the execution of any DDL command:

CREATE OR REPLACE FUNCTION abort_any_command()
\n
  RETURNS event_trigger
\n
 LANGUAGE plpgsql
\n
  AS $$
BEGIN
\n
  RAISE EXCEPTION 'command % is disabled', tg_tag;
END;
$$;
CREATE EVENT TRIGGER abort_ddl ON ddl_command_start
\n
   EXECUTE FUNCTION abort_any_command();

COMPATIBILITY#

There is no CREATE EVENT TRIGGER statement in the SQL standard.

SEE ALSO#

ALTER EVENT TRIGGER (ALTER_EVENT_TRIGGER(7)), DROP EVENT TRIGGER (DROP_EVENT_TRIGGER(7)), CREATE FUNCTION (CREATE_FUNCTION(7))