| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Henk van Lingen <H(dot)G(dot)K(dot)vanLingen(at)uu(dot)nl> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Forcing the right queryplan |
| Date: | 2010-09-09 15:16:36 |
| Message-ID: | 29669.1284045396@sss.pgh.pa.us |
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| Lists: | pgsql-general pgsql-novice |
Henk van Lingen <H(dot)G(dot)K(dot)vanLingen(at)uu(dot)nl> writes:
> On Thu, Sep 09, 2010 at 10:50:52AM -0400, Tom Lane wrote:
>>>> Well, there's your problem: the planner is off by a factor of about 500
>>>> on its estimate of the number of rows matching this query, and that's
>>>> what's causing it to pick the wrong plan. What you need to look into
>>>> is getting that estimate to be more in sync with reality. Probably
>>>> increasing the stats target for the message column would help.
> But how can I get sane estimates for syslog data? Some searchstrings will
> result in only a few hits, others in thousands of records or more.
That's what ANALYZE is for ...
regards, tom lane
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