CREATE EVENT TRIGGER (original) (raw)

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CREATE EVENT TRIGGER — define a new event trigger

Synopsis

CREATE EVENT TRIGGER name ON event [ WHEN filtervariable IN (filtervalue [, ... ]) [ AND ... ] ] EXECUTE PROCEDURE functionname()

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 39. 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 39.1 for more information on event names.

filtervariable

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 filtervariable is TAG.

filtervalue

A list of values for the associated filtervariable for which the trigger should fire. For TAG, this means a list of command tags (e.g., 'DROP FUNCTION').

functionname

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 BEGINRAISEEXCEPTION′commandEND;BEGIN RAISE EXCEPTION 'command % is disabled', tg_tag; END;BEGINRAISEEXCEPTION′commandEND;;

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.