IMO, composite types on insert/update should work as they do on select:
SELECT foo FROM foo; -- works, returning type foo
INSERT INTO foo VALUES '(something)'::foo -- fails,
but we have a workaround:
INSERT INTO foo SELECT ('(something)'::foo).* -- expands foo into foo columns
however no such workaround exists for update. ideally,
UPDATE foo SET foo = foo;
would be valid. Aside from fixing a surprising behavior, it would
greatly aid in writing triggers that do things like ship updates over
dblink _much_ easier (in fact...the dblink_build_xxx family would
become obsolete).
e.g.
perform dblink.dblink('UPDATE foo SET foo = \'' || new || '\'::foo);
I call the existing behavior of insert/update of composite types
broken to the point of almost being a bug. Fixing the above to work
would close the loop on a broad new set of things you can do with
composite types.
merlin
