Re: 9a57858f1103b89a5674f0d50c5fe1f756411df6

On Thu, 2014-03-13 at 12:00 +0100, Andres Freund wrote:
> On 2014-03-12 20:09:23 -0400, Robert Haas wrote:
> > On the pgsql-packagers list, there has been some (OT for that list)
> > discussion of whether commit 9a57858f1103b89a5674f0d50c5fe1f756411df6
> > is sufficiently serious to justify yet another immediate minor release
> > of 9.3.x. The relevant questions seem to be:
> >
> > 1. Is it really bad?
>
> It breaks the ctid of concurrently updated/locked tuples during WAL
> replay. Which can lead to all sorts of nastiness like indexes not
> finding any rows. Since that kind of locking/updating is pretty common
> with foreign keys, it's not an unlikely scenario.
> Unfortunately FPIs won't save the day in all that many scenarios because
> there'll normally a XLOG_HEAP2_LOCK_UPDATED before the XLOG_HEAP_LOCK
> record which is replayed badly.
>
> Now, one could argue that it only affects replicas or servers that
> crashed at some point, but I think that's not much comfort.
>
> > 2. Does it affect a lot of people or only a few?
>
> It's been reported twice (Peter Geoghegan, Greg Stark) by Heroku and one
> person on IRC could reproduce it repeatedly. The latter was what made me
> look into it again and find the bug. Greg has confirmed that it fixes
> the bug when replaying the WAL again.
>
> > 3. Are there more, equally bad bugs that are unfixed, or perhaps even
> > unreported, yet?
>
> Uh. I have no idea. I don't know of any reports that can't be attributed
> to any of these, but as you're also include unreported bugs in that
> question...
>

Does this affect also other branches? 9.2 ?

regards,
--
Jozef Mlich <jmlich(at)redhat(dot)com>
Associate Software Engineer - EMEA ENG Developer Experience
Mobile: +420 604 217 719
http://cz.redhat.com/
Red Hat, Inc.