Re: Domains and subtypes, a brief proposal

elein <elein@varlena.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