9.28. Event Trigger Functions

Currently PostgreSQL provides one built-in event trigger helper function, pg_event_trigger_dropped_objects.

pg_event_trigger_dropped_objects returns a list of all object dropped by the command in whose sql_drop event it is called. If called in any other context, pg_event_trigger_dropped_objects raises an error. pg_event_trigger_dropped_objects returns the following columns:

The pg_event_trigger_dropped_objects function can be used in an event trigger like this:

CREATE FUNCTION test_event_trigger_for_drops()
        RETURNS event_trigger LANGUAGE plpgsql AS $$
DECLARE
    obj record;
BEGIN
    FOR obj IN SELECT * FROM pg_event_trigger_dropped_objects()
    LOOP
        RAISE NOTICE '% dropped object: % %.% %',
                     tg_tag,
                     obj.object_type,
                     obj.schema_name,
                     obj.object_name,
                     obj.object_identity;
    END LOOP;
END
$$;
CREATE EVENT TRIGGER test_event_trigger_for_drops
   ON sql_drop
   EXECUTE PROCEDURE test_event_trigger_for_drops();

For more information about event triggers, see Chapter 37.