Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?

From: Bryce Nesbitt <bryce2(at)obviously(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Re: 512,600ms query becomes 7500ms... but why? Postgres 8.3 query planner quirk?
Date: 2010-02-13 07:55:07
Message-ID: 4B765ADB.5060305@obviously.com
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Tom Lane wrote:
> Given that it estimated 1 row out of "words" (quite correctly) and 12264
> rows out of each scan on article_words, you'd think that the join size
> estimate would be 12264, which would be off by "only" a factor of 3 from
> the true result. Instead it's 23, off by a factor of 200 :-(.
>
Has anyone every proposed a "learning" query planner? One that
eventually clues in to estimate mismatches like this?

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