Re: 9.2beta1, parallel queries, ReleasePredicateLocks, CheckForSerializableConflictIn in the oprofile

On Fri, May 25, 2012 at 10:22 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Merlin Moncure <mmoncure(at)gmail(dot)com> writes:
>> Hm, what if BufTableHashPartition() was pseudo randomized so that
>> different backends would not get the same buffer partition for a
>> particular tag?
>
> Huh?  You have to make sure that different backends will find the same
> buffer for the same page, so I don't see how that can possibly work.

Right -- duh. Well, hm. Is this worth fixing? ISTM there's a bit of
'optimizing for pgbench-itis' in the buffer partitions -- they seem
optimized to lever the mostly random access behavior of pgbench. But
how likely is it to see multiple simultaneous scans in the real world?
Interleaving scans like that is not a very effective optimization --
if it was me, it'd be trying to organize something around a
partitioned tid scan for parallel sequential access.

merlin