Re: Domains and subtypes, a brief proposal

elein <elein(at)varlena(dot)com> writes:
> Domains and subtypes.

> * Create new child type from values in parent type.
> * Maintain only checks for constraints
> * Create implicit casts from child to parent

This seems a bit content-free, because it's not clear how it differs
from what we do now. We already have implicit child-to-parent casts.

> Constraints on types:

> * Change the pg_types to hold a NULLABLE constraint text column
> OR add a type constraint lookup table (pg_domains?)

I understand that you are arguing to allow constraints to be associated
with any type not only domains, but
(a) I don't see why we should want to add that overhead, and
(b) I don't see what that has to do with the problem you actually
need to solve, specifically limiting the application of implicit
domain-to-base-type casts.

regards, tom lane