Re: Revisiting default_statistics_target

On 5/22/09 2:36 PM, Tom Lane wrote:
> andrew@dunslane.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