Re: ALTER TABLE ... ADD FOREIGN KEY ... NOT ENFORCED

Robert Haas <robertmhaas@gmail.com> writes:
> ...  On the
> other hand, there's clearly also a use case for this behavior.  If a
> bulk load of prevalidated data forces an expensive revalidation of
> constraints that are already known to hold, there's a real chance the
> DBA will be backed into a corner where he simply has no choice but to
> not use foreign keys, even though he might really want to validate the
> foreign-key relationships on a going-forward basis.

There may well be a case to be made for doing this on grounds of
practical usefulness.  I'm just voicing extreme skepticism that it can
be supported by reference to the standard.

Personally I'd prefer to see us look into whether we couldn't arrange
for low-impact establishment of a verified FK relationship, analogous to
CREATE INDEX CONCURRENTLY.  We don't let people just arbitrarily claim
that a uniqueness condition exists, and ISTM that if we can handle that
case we probably ought to be able to handle FK checking similarly.
        regards, tom lane