From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
Cc: | Dharmendra Goyal <dharmendra(dot)goyal(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: second DML operation fails with updatable cursor |
Date: | 2007-10-24 18:35:53 |
Message-ID: | 10326.1193250953@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Heikki Linnakangas <heikki(at)enterprisedb(dot)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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