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Re: Wrong rows count estimation (explain, gist, tsearch)

From: Sergey Konoplev <gray(dot)ru(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Wrong rows count estimation (explain, gist, tsearch)
Date: 2009-09-28 15:17:31
Message-ID: c3a7de1f0909280817u4b97aa38v78b4434b25eb0583@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-general
On Mon, Sep 28, 2009 at 6:26 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Sergey Konoplev <gray(dot)ru(at)gmail(dot)com> writes:
>> The table filled with about 7.5E+6 rows. Most of them have different
>> from default values in obj_tsvector column. I use "estimated rows
>> count trick" to make search results counter faster, and every time
>> when obj_tsvector is used estimation rows count is extremely differ
>> from actual (eg. 6821 vs 372012). I played with SET STATISTICS but
>> have no success.
>
> 8.3 has just a stub estimator for @@.  You might have better results
> with 8.4.  In the particular example you're showing, though, I don't
> think the poor rowcount estimate is making any difference to the
> plan choice.

Thanx, Tom. Will try 8.4

>
>                        regards, tom lane
>



-- 
Regards,
Sergey Konoplev
--
PostgreSQL articles in english & russian
http://gray-hemp.blogspot.com/search/label/postgresql/

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