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Re: Optimization idea

From: Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Vlad Arkhipov <arhipov(at)dc(dot)baikal(dot)ru>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimization idea
Date: 2010-04-23 13:09:34
Message-ID: q2ne94e14cd1004230609u9596f80ve2d126430be8cd86@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
2010/4/23 Robert Haas <robertmhaas(at)gmail(dot)com>:
> On Thu, Apr 22, 2010 at 10:37 PM, Vlad Arkhipov <arhipov(at)dc(dot)baikal(dot)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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