Re: bogus error message for ALTER TABLE ALTER CONSTRAINT

=?utf-8?Q?=C3=81lvaro?= Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> I just discovered that trying to set a foreign key as NO INHERIT in
> ALTER TABLE ALTER CONSTRAINT returns an absurd error message:
> create table pk (a int primary key);
> create table fk (a int references pk);
> alter table fk alter constraint fk_a_fkey deferrable, alter constraint fk_a_fkey no inherit;
> ERROR: ALTER CONSTRAINT statement constraints cannot be marked NO INHERIT

> The explanation is that somebody misunderstood what must be given to
> processCASbits in 2013. The intended message is:
> ERROR: FOREIGN KEY constraints cannot be marked NO INHERIT

Hmm. I agree that "ALTER CONSTRAINT statement" is off the
mark here, but I'm not convinced that "FOREIGN KEY" is entirely
on-point either. The grammar has no way of knowing what kind of
constraint is being targeted. I do see that ATExecAlterConstraint
currently rejects every other kind of constraint, but do we need
to think of a more generic phrase?

regards, tom lane