typecmds.c says:
"Domains over composite types might be made to work in the future, but
not today."
Attached is a patch that allows domains over composite types, together
with test cases in domaincomp.sql. A domain over a composite type has
typtype TYPTYPE_DOMAIN, but typrelid and typrelkind are empty: that
information is only available in the pg_type record of the base type.
The remainder of the patch follows from that choice. While parsing a
record expression into a row type, an extra coercion node had to be
inserted to ensure that the domain checks are called.
All regression tests are ok, comments are highly appreciated.
--
Yeb Havinga
http://www.mgrid.net/
Mastering Medical Data