Re: Simple postgresql.conf wizard

From: Decibel! <decibel(at)decibel(dot)org>
To: Gregory Stark <stark(at)enterprisedb(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "Dann Corbit" <DCorbit(at)connx(dot)com>, "Robert Haas" <robertmhaas(at)gmail(dot)com>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "Mark Wong" <markwkm(at)gmail(dot)com>, "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, "Josh Berkus" <josh(at)agliodbs(dot)com>, "Greg Smith" <gsmith(at)gregsmith(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Simple postgresql.conf wizard
Date: 2008-11-26 19:25:56
Message-ID: C4A88488-F42C-4FB4-AB92-D1346BE92B54@decibel.org
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On Nov 25, 2008, at 7:06 PM, Gregory Stark wrote:
>> The thought occurs to me that we're looking at this from the
>> wrong side of the
>> coin. I've never, ever seen query plan time pose a problem with
>> Postgres, even
>> without using prepared statements.
>
> I certainly have seen plan times be a problem. I wonder if you have
> too and
> just didn't realize it. With a default_stats_target of 1000 you'll
> have
> hundreds of kilobytes of data to slog through to plan a moderately
> complex
> query with a few text columns. Forget about prepared queries, I've
> seen plan
> times be unusable for ad-hoc interactive queries before.

Can you provide any examples?

And no, I've never seen a system where a few milliseconds of plan
time difference would pose a problem. I'm not saying they don't
exist, only that I haven't seen them (including 2 years working as a
consultant).

I'll also make the argument that anyone with a system that does have
those kind of requirements will have also needed to actually tune
their config, and tune it well. I can't see them being bothered by
having to set one more parameter. There are a lot of systems that are
being impacted by our ultra-low stats target, and a lot of those
don't necessarily need a lot of hand tuning beyond the stats target.
--
Decibel!, aka Jim C. Nasby, Database Architect decibel(at)decibel(dot)org
Give your computer some brain candy! www.distributed.net Team #1828

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