| From: | Greg Stark <gsstark(at)mit(dot)edu> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Markus Wanner <markus(at)bluegap(dot)ch>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: determine snapshot after obtaining locks for first statement |
| Date: | 2009-12-17 17:49:11 |
| Message-ID: | 407d949e0912170949n5f16d13are2f8f8c1eddf4b8b@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Dec 17, 2009 at 5:39 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Well, it would all depend on what you're trying to do. Typical
> single-row UPDATE commands aren't really affected by this problem,
> and in fact the behavior is pretty much exactly what they want as
> long as the WHERE conditions don't involve columns that are being
> changed.
>
> Maybe we should replace the bit about "complex search conditions"
> with something about referencing multiple rows to perform one update.
> I'm not very sure what a clearer explanation would look like though.
I wonder if RETURNING hasn't created a whole new set of cases where
our READ COMMITTED behaviour is bogus. I guess it's equivalent to
having used SELECT FOR UPDATE.
--
greg
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