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 objects 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:
| Name | Type | Description |
|---|---|---|
| classid | Oid | OID of catalog the object belonged in |
| objid | Oid | OID the object had within the catalog |
| objsubid | int32 | Object sub-id (e.g. attribute number for columns) |
| object_type | text | Type of the object |
| schema_name | text | Name of the schema the object belonged in, if any; otherwise NULL. No quoting is applied. |
| object_name | text | Name of the object, if the combination of schema and name can be used as an unique identifier for the object; otherwise NULL. No quoting is applied, and name is never schema-qualified. |
| object_identity | text | Text rendering of the object identity, schema-qualified. Each and every identifier present in the identity is quoted if necessary. |
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 Глава 37.