Re: More FOR UPDATE/FOR SHARE problems
От | Jeff Davis |
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Тема | Re: More FOR UPDATE/FOR SHARE problems |
Дата | |
Msg-id | 1233769274.29523.25.camel@jdavis обсуждение исходный текст |
Ответ на | Re: More FOR UPDATE/FOR SHARE problems (Bruce Momjian <bruce@momjian.us>) |
Ответы |
Re: More FOR UPDATE/FOR SHARE problems
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Список | pgsql-hackers |
On Wed, 2009-02-04 at 11:11 -0500, Bruce Momjian wrote: > Well, with no one replying, :-(, I went ahead and added to the Read > Committed section of our manual to show a simple case where our read > committed mode produces undesirable results. I also did a little > cleanup at the same time. We could also add something to the SELECT docs. For example: "FOR SHARE/UPDATE causes the SELECT to behave with the same isolation semantics as UPDATE or DELETE. You may see results that are impossible to see using SELECT without FOR UPDATE/SHARE. See Chapter 13." The current SELECT FOR UPDATE/SHARE docs do address the issue, but most of the discussion revolves around locking semantics, not isolation. I think the important missing piece is "...you may see results that are impossible to see using SELECT...". I've learned a few things during this discussion, but the most surprising thing to me was that FOR SHARE/UPDATE really change the isolation semantics, and that it's more like UPDATE than SELECT. Regards,Jeff Davis
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