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Re: Deadlock bug

Josh Berkus <josh@agliodbs.com>

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From: Josh Berkus <josh@agliodbs.com>
To: Simon Riggs <simon@2ndQuadrant.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Greg Stark <gsstark@mit.edu>, Nicolas Barbier <nicolas.barbier@gmail.com>, Markus Wanner <markus@bluegap.ch>, pgsql-hackers@postgresql.org
Date: 2010-08-25T22:56:05Z
Lists: pgsql-hackers 
On 8/25/10 1:35 PM, Simon Riggs wrote:
> If the row is "key share" locked (as opposed to "tuple share" locks we
> already have), then an UPDATE would only work if it was a non-HOT
> UPDATE. Yes, that would save us some effort in working out whether to
> allow the UPDATE or not. It *is* more restrictive than strictly
> necessary, but much better than the current situation. So at least we
> know that part of it has an easy solution.

I agree that this would be an improvement.

It still has the issue of being baffling to users (why did I get a
deadlock this time, and not THAT time?) but current behavior has that
problem.  Heck, current behavior is often baffling to *me*.

The other thing which came out of this incident (and many user reports)
is the rather extreme opacity of our locking information, despite the
improvements of the last 2 versions.  However, I don't have a proposal
on how that should be fixed .... yet.

-- 
                                  -- Josh Berkus
                                     PostgreSQL Experts Inc.
                                     http://www.pgexperts.com