Automatically deleting dangling large object references.

I was thinking of trying something like the following to automatically delete
rows from tables that reference large objects when the large object is
unlinked. It would depend on pg_class having a PRIMARY key (on the hidden
'oid' column in this possible example):

-- this is a generic table to just hold large objects
CREATE TABLE lobjs (
id SERIAL CONSTRAINT lobjs_id_con
PRIMARY KEY,
-- other tables referencing this would also react.
lo_oid OID CONSTRAINT lobjs_lo_oid_con NOT NULL,
-- holds an actual large object id.
lo_ref_oid OID CONSTRAINT lobjs_lo_ref_oid_con
REFERENCES pg_class
ON UPDATE CASCADE
ON DELETE CASCADE
INITIALLY DEFERRED
);

CREATE RULE set_lo_ref_oid AS
ON INSERT TO lobjs
DO
UPDATE lobjs
SET lo_ref_oid = pg_class.oid
FROM pg_class
WHERE pg_class.relname = "xinx" || new.lo_oid;

Something like that (I'd have to check this sql to make sure its right). I don't
think there is a primary key on the system tables. I wonder if it would cause
problems if there where?

Anyway, does anyone know of a way to accomplish something like what I am trying
to do with the large objects?

--
Robert B. Easter
reaster(at)comptechnews(dot)com