From: | Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com> |
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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 |
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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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