Name
CREATE EVENT TRIGGER -- define a new event triggerSynopsis
CREATE EVENT TRIGGER name ON event [ WHEN filter_variable IN (filter_value [, ... ]) [ AND ... ] ] EXECUTE 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
isTAG
. filter_value
-
A list of values for the associated
filter_variable
for which the trigger should fire. ForTAG
, 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
.
Notes
Only superusers can create event triggers.
Event triggers are disabled in single-user mode (see postgres). 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.
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 PROCEDURE abort_any_command();
Compatibility
There is no CREATE EVENT TRIGGER
statement in the SQL standard.
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