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help / color / mirror / Atom feedFrom: Joshua D. Drake <[email protected]>
To: Tom Lane <[email protected]>
Cc: Heikki Linnakangas <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Simon Riggs <[email protected]>
Cc: [email protected]
Cc: [email protected]
Subject: Re: FOR SHARE vs FOR UPDATE locks
Date: Fri, 01 Dec 2006 10:54:38 -0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
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On Fri, 2006-12-01 at 13:46 -0500, Tom Lane wrote:
> "Heikki Linnakangas" <[email protected]> writes:
> > Let's throw an error for now. We have to come back to this in 8.3, I think.
>
> After further thought I think we should also seriously consider plan C:
> do nothing for now. We now realize that there have been related bugs
> since 8.0, namely that
>
> begin;
> select some rows for update;
> savepoint x;
> update the same rows;
> rollback to x;
>
> leaves the tuple(s) not locked. The lack of complaints about this from
> the field suggests that this isn't a huge problem in practice. If we
> do make it throw an error I'm afraid that we will break applications
> that aren't having a problem at the moment.
>
> I'm also realizing that a fix along the throw-an-error line is
> nontrivial, eg, HeapTupleSatisfiesUpdate would need another return code.
>
> So at this point we are facing three options:
> - throw in a large and poorly tested "fix" at the last moment;
> - postpone 8.2 until we can think of a real fix, which might
> be a major undertaking;
> - ship 8.2 with the same behavior 8.0 and 8.1 had.
> None of these are very attractive, but I'm starting to think the last
> is the least bad.
/me struggles...
IMHO:
option 2 is the correct option, but the least favorable.
option 1 is probably bad
option 3 is the lesser of the evils if we document it loudly.
Joshua D. Drake
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
>
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