[PATCH] Add pg_get_event_trigger_ddl() function

Hi

Attached is a patch implementing a function to generate the DDL for a CREATE
EVENT TRIGGER statement. This complements existing similar functions
(pg_get_database_ddl(), pg_get_role_ddl() etc.).

Patch includes regression test and documentation.

Example:

CREATE OR REPLACE FUNCTION forbid_table_rewrites()
RETURNS event_trigger
LANGUAGE plpgsql
AS $$
BEGIN
RAISE EXCEPTION 'command % prohibited', tg_tag;
END;
$$;

CREATE EVENT TRIGGER forbid_rewrites
ON table_rewrite
WHEN tag IN ('ALTER TABLE', 'ALTER MATERIALIZED VIEW')
EXECUTE FUNCTION forbid_table_rewrites();

SELECT pg_get_event_trigger_ddl('forbid_rewrites');

postgres=# SELECT pg_get_event_trigger_ddl('forbid_rewrites',true);
pg_get_event_trigger_ddl
------------------------------------------------------------
CREATE EVENT TRIGGER forbid_rewrites +
ON table_rewrite +
WHEN TAG IN ('ALTER TABLE', 'ALTER MATERIALIZED VIEW')+
EXECUTE FUNCTION public.forbid_table_rewrites();
(1 row)

Regards

Ian Barwick