Jeff Davis <pgsql(at)j-davis(dot)com> writes:
> Is it a problem to allow unique constraints to be deferrable until the
> end of the command though?
Yes. If you do have a case where this matters, the command updating the
referenced table is most likely different from the one updating the
referencing table, and so the command boundaries aren't the same.
I think what we can do for now is insist that the FK's unique constraint
be immediate-mode. Trying to relax that looks like a research project
to me.
regards, tom lane