CREATE EVENT TRIGGER(7) PostgreSQL 17.4 Documentation CREATE EVENT TRIGGER(7)
NAME
CREATE_EVENT_TRIGGER - define a new event trigger
SYNOPSIS
CREATE EVENT TRIGGER name
ON event
[ WHEN filter_variable IN (filter_value [, ... ]) [ AND ... ] ]
EXECUTE { FUNCTION | PROCEDURE } function_name()
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
The name to give the new trigger. This name must be unique within
the database.
event
The name of the event that triggers a call to the given function.
See Section 38.1 for more information on event names.
filter_variable
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
filter_variable is TAG.
filter_value
A list of values for the associated filter_variable for which the
trigger should fire. For TAG, this means a list of command tags
(e.g., 'DROP FUNCTION').
function_name
A user-supplied function that is declared as taking no argument and
returning type event_trigger.
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()
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 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))
PostgreSQL 17.4 2025 CREATE EVENT TRIGGER(7)
postgresql 17.4 - Generated Sat Mar 22 13:41:17 CDT 2025