Re: second DML operation fails with updatable cursor - Mailing list pgsql-hackers

From Tom Lane
Subject Re: second DML operation fails with updatable cursor
Date
Msg-id 10326.1193250953@sss.pgh.pa.us
Whole thread Raw
In response to Re: second DML operation fails with updatable cursor  (Heikki Linnakangas <heikki@enterprisedb.com>)
Responses Re: second DML operation fails with updatable cursor
List pgsql-hackers
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


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