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...
Greetings,
Andres Freund
-- Andres Freund http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services