Re: [HACKERS] Re: ALTER TABLE DROP COLUMN

> ALL the FK triggers are delayed until after the entire
> statement (what's wrong for ON DELETE RESTRICT - but that's
> another story), or until the entire transaction (in deferred
> mode).
>
> But the UNIQUE constraint is still built upon unique nbtree
> indices, thus failing on primary key where such a unique
> index is automatically created for.
>
> I'm far too less familiar with our implementation of nbtree
> to tell whether it would be possible at all to delay unique
> checking until statement end or XACT commit. At least I
> assume it would require some similar technique of deferred
> queue.

We might want to look at what we're doing for all of the constraints,
because at some point we'll probably want to let you defer the other
constraints as well (I'm pretty sure this technically legal in SQL92).
If we can think of a good way to handle all of the constraints together
that might be worth doing to prevent us from coding the same thing
multiple times.