Jeff Davis <pgsql@j-davis.com> writes:
> My question is not why don't we allow subqueries in CHECK, my question
> is why do we allow stable/volatile functions?
Historically we've allowed it, and it's not clear what we'd buy by
changing that, other than breaking existing applications whose authors
forgot to mark their functions immutable. If there were something we
could usefully do by checking the mutability status of the condition,
then it would be worth breaking compatibility here...
regards, tom lane