| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | andrew(at)dunslane(dot)net, Greg Smith <gsmith(at)gregsmith(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Revisiting default_statistics_target |
| Date: | 2009-05-22 19:32:01 |
| Message-ID: | 4A16FDB1.6060207@agliodbs.com |
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| Thread: | |
| Lists: | pgsql-hackers |
On 5/22/09 2:36 PM, Tom Lane wrote:
> andrew(at)dunslane(dot)net writes:
>> Wouldn't he just need to rerun the tests with default_stats_target set to
>> the old value? I presume he has actually done this already in order to
>> come to the conclusion he did about the cause of the regression.
>
> Yeah, he did, so we know it's slower that way. But exactly *why* it's
> slower is not proven. It could be an artifact rather than something
> we really ought to react to.
It appears (right now) to be an artifact.
The drop in performance happens with queries which are called using C
stored procedures exclusively. It doesn't show up on other benchmarks
which call similar queries directly.
Jignesh and I will be testing some stuff next week to get a better idea
of what exactly makes the drop happen, but for not this appears to be a
corner case.
--
Josh Berkus
PostgreSQL Experts Inc.
www.pgexperts.com
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