| PostgreSQL 9.4.5 Documentation | |||
|---|---|---|---|
| Prev | Up | Chapter 9. Functions and Operators | Next | 
    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 a 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 Chapter 37.