Re: More FOR UPDATE/FOR SHARE problems

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.