| From: | Mark Kirkwood <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> |
|---|---|
| To: | Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com> |
| Cc: | Jim Nasby <jim(at)nasby(dot)net>, Greg Stark <stark(at)mit(dot)edu>, Josh Berkus <josh(at)agliodbs(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: ANALYZE sampling is too good |
| Date: | 2013-12-10 00:14:00 |
| Message-ID: | 52A65CC8.4070805@catalyst.net.nz |
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| Lists: | pgsql-hackers |
On 10/12/13 12:14, Heikki Linnakangas wrote:
>
>
> I took a stab at using posix_fadvise() in ANALYZE. It turned out to be
> very easy, patch attached. Your mileage may vary, but I'm seeing a
> nice gain from this on my laptop. Taking a 30000 page sample of a
> table with 717717 pages (ie. slightly larger than RAM), ANALYZE takes
> about 6 seconds without the patch, and less than a second with the
> patch, with effective_io_concurrency=10. If anyone with a good test
> data set loaded would like to test this and post some numbers, that
> would be great.
>
>
I did a test run:
pgbench scale 2000 (pgbench_accounts approx 25GB).
postgres 9.4
i7 3.5Ghz Cpu
16GB Ram
500 GB Velociraptor 10K
(cold os and pg cache both runs)
Without patch: ANALYZE pgbench_accounts 90s
With patch: ANALYZE pgbench_accounts 91s
So I'm essentially seeing no difference :-(
Regards
Mark
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