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 | 1232990796.3045.76.camel@jdavis обсуждение исходный текст |
Ответ на | Re: More FOR UPDATE/FOR SHARE problems ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>) |
Ответы |
Re: More FOR UPDATE/FOR SHARE problems
Re: More FOR UPDATE/FOR SHARE problems |
Список | pgsql-hackers |
On Mon, 2009-01-26 at 10:48 -0600, Kevin Grittner wrote: > I guess the issue of whether this violation of ACID properties should > be considered a bug or a feature is a separate discussion, but calling > it a feature seems like a hard sell to me. > I think I understand the other perspective on this now: SELECT FOR UPDATE/SHARE is an entirely separate command that is more similar (in transactional semantics) to UPDATE than to SELECT. In fact, it's probably most similar to UPDATE ... RETURNING, which will give the same result (that breaks atomicity or isolation, depending on your point of view), which is correct for READ COMMITTED isolation level. Because the command begins with SELECT, I would expect it to follow the rules of SELECT with the side effect of locking. I would think that the standard would have something to say about this*. I certainly don't think it's intuitive behavior. Regards,Jeff Davis. *: It appears that SELECT ... FOR UPDATE is not in the standard, which would indicate to me that the SELECT statement should still behave according to SELECT isolation/snapshot rules. But when I guess about the standard, I'm usually wrong.
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