Re: second DML operation fails with updatable cursor

Heikki Linnakangas <heikki@enterprisedb.com> writes:
> Yes, re-fetching row you just deleted is supposed to raise an error.
> That doesn't seem very hard to implement. If an UPDATE/DELETE CURRENT OF
> doesn't find the tuple to update/delete, raise an error.

Uh, no, the error would have to come from FETCH RELATIVE 0, and there's
a problem because no single piece of the code has all the facts needed
to know that an error should be thrown.  I don't currently see any
non-klugy way to detect that.

It might make sense to go with Simon's suggestion to just forbid
non-forwards fetch from a FOR UPDATE cursor (assuming that we agree he's
read the spec correctly to disallow that).  That would mask the problem
cases in a clean way, and we could fix them sometime later as an
enhancement, if anyone finds it worthwhile.
        regards, tom lane