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

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Florian Pflug <fgp@phlo.org>
Cc: Merlin Moncure <mmoncure@gmail.com>, Sergey Koposov <koposov@ast.cam.ac.uk>, Jeff Janes <jeff.janes@gmail.com>, pgsql-hackers@postgresql.org, Stephen Frost <sfrost@snowman.net>
Date: 2012-06-01T17:51:11Z
Lists: pgsql-hackers

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

On Fri, Jun 1, 2012 at 8:47 AM, Florian Pflug <fgp@phlo.org> wrote:
> A simpler idea would be to collapse UnpinBuffer() / PinBuffer() pairs
> by queing UnpinBuffer() requests for a while before actually updating
> shared state.

So, what happens when somebody wants a cleanup lock on the buffer
you've decided to keep pinned?  We have this problem already; I'm wary
of making it worse.

> We'd drain the unpin queue whenever we don't expect a PinBuffer() request
> to happen for a while. Returning to the main loop is an obvious such place,
> but there might be others.

However, on a workload like pgbench -S, dropping the pin when you
return to the main loop would render the optimization useless.

-- 
Robert Haas
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