Horton

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

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Merlin Moncure <mmoncure@gmail.com>, Sergey Koposov <koposov@ast.cam.ac.uk>, pgsql-hackers@postgresql.org
Date: 2012-05-24T22:16:46Z
Lists: pgsql-hackers

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  1. Improve bulk-insert performance by keeping the current target buffer pinned

Robert Haas <robertmhaas@gmail.com> writes:
> On Thu, May 24, 2012 at 4:46 PM, Merlin Moncure <mmoncure@gmail.com> wrote:
>> We don't get to skip wal of course, but we should be able to use a
>> bulk insert strategy, especially if there was some way of predicting
>> that a large number of tuples were going to be inserted. I'm
>> wondering though of contention on the free list is in fact the OP's
>> problem.

> Not sure.  It might be some other LWLock, but it's hard to tell which
> one from the information provided.

Yeah.  It seems quite plausible that Robert's select-only benchmark might
be mainly tripping over the freelist lock, but I'm less convinced about
something that's doing INSERT/SELECT, and therefore is also doing a lot
of WAL activity, index insertions, etc.  I'd want to see some
instrumentation results before assuming we know where the bottleneck is
there.

			regards, tom lane