From: Robert Haas <robertmhaas@gmail.com>
To: Cédric Villemain <cedric.villemain.debian@gmail.com>
Cc: Vlad Arkhipov <arhipov@dc.baikal.ru>
Cc: pgsql-performance@postgresql.org
Subject: Re: Optimization idea
Date: Fri, 23 Apr 2010 09:36:40 -0400
Message-ID: <h2z603c8f071004230636zaec7edf2y2cbc0847ba17cd51@mail.gmail.com> (raw)
In-Reply-To: <q2ne94e14cd1004230609u9596f80ve2d126430be8cd86@mail.gmail.com>
References: <4BD0161A.4010908@dc.baikal.ru>
<4BD0430C.1050308@2ndquadrant.com>
<4BD10805.9060004@dc.baikal.ru>
<y2y603c8f071004230405r5fcef546l3da84c407ce2655a@mail.gmail.com>
<q2ne94e14cd1004230609u9596f80ve2d126430be8cd86@mail.gmail.com>
On Fri, Apr 23, 2010 at 9:09 AM, Cédric Villemain
<cedric.villemain.debian@gmail.com> wrote:
> 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.
Well, what do you think the planner should do differently?
...Robert
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To: pgsql-performance@postgresql.org
Cc: robertmhaas@gmail.com, cedric.villemain.debian@gmail.com, arhipov@dc.baikal.ru
Subject: Re: Optimization idea
In-Reply-To: <h2z603c8f071004230636zaec7edf2y2cbc0847ba17cd51@mail.gmail.com>
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