Re: TODO: Fix CREATE CAST on DOMAINs

Tom Lane wrote:
> Now we do have the flexibility to alter the default contents of pg_cast
> --- there could be more or fewer entries in there than there are now,
> if the type coercion rules are altered to do less or more automatically
> than they do now. But the end-result behavior needs to wind up being
> pretty darn near the same thing, at least within the numeric type
> category (I'm not as certain that we have the other ones right, but the
> numeric category has been *very* heavily scrutinized and beat upon).
> The only thing I really want to see changing is the behavior for domain
> types --- and even there, the "default" behavior when there are no
> user-created domain-specific operators or casts has to stay the same.

Your suggestion upthread that domains have two-step casts (from domain to base,
then from base to whatever) is what got my attention. I don't like the idea of
having an interim solution to that subset of the problem if it might get in the
way of solving the general problem later. But perhaps it can be argued that no
cruftiness would result from the special case code for casting domains to their
base types?

mark