From: Cédric Villemain <cedric.villemain.debian@gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Vlad Arkhipov <arhipov@dc.baikal.ru>
Cc: pgsql-performance@postgresql.org
Subject: Re: Optimization idea
Date: Fri, 23 Apr 2010 15:09:34 +0200
Message-ID: <q2ne94e14cd1004230609u9596f80ve2d126430be8cd86@mail.gmail.com> (raw)
In-Reply-To: <y2y603c8f071004230405r5fcef546l3da84c407ce2655a@mail.gmail.com>
References: <4BD0161A.4010908@dc.baikal.ru>
<4BD0430C.1050308@2ndquadrant.com>
<4BD10805.9060004@dc.baikal.ru>
<y2y603c8f071004230405r5fcef546l3da84c407ce2655a@mail.gmail.com>
2010/4/23 Robert Haas <robertmhaas@gmail.com>:
> On Thu, Apr 22, 2010 at 10:37 PM, Vlad Arkhipov <arhipov@dc.baikal.ru> wrote:
>> I don't think this is just an issue with statistics, because the same
>> problem arises when I try executing a query like this:
>
> I'm not sure how you think this proves that it isn't a problem with
> statistics, but I think what you should be focusing on here, looking
> back to your original email, is that the plans that are actually much
> faster have almost as much estimated cost as the slower one. Since
> all your data is probably fully cached, at a first cut, I might try
> setting random_page_cost and seq_page_cost to 0.005 or so, and
> adjusting effective_cache_size to something appropriate.
that will help worrect the situation, but the planner is loosing here I think.
>
> ...Robert
>
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--
Cédric Villemain
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To: pgsql-performance@postgresql.org
Cc: cedric.villemain.debian@gmail.com, robertmhaas@gmail.com, arhipov@dc.baikal.ru
Subject: Re: Optimization idea
In-Reply-To: <q2ne94e14cd1004230609u9596f80ve2d126430be8cd86@mail.gmail.com>
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