Re: SELECT performance problem on a join

From: David Olbersen <dave(at)slickness(dot)org>
To: Patrice Espié <patrice(dot)espie(at)univ-lyon2(dot)fr>
Cc: <pgsql-novice(at)postgresql(dot)org>
Subject: Re: SELECT performance problem on a join
Date: 2001-04-25 16:43:05
Message-ID: Pine.LNX.4.31.0104250941380.5321-100000@bubbles.electricutopia.net
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On Wed, 25 Apr 2001, Patrice Espié wrote:

> Hello,
>
> I have a great problem with performances of my database, on the SQL request:
> ---------------
> select t_test.doc_id, t_test.f_num_centre, t_test.f_num_candidat from
> t_test, doc where t_test.doc_id=doc.id and doc.docsubset_id=2000077392
> ---------------
> The doc table has 36.000 rows, and t_test the same. There is an index on doc
> (docsubset_id) and an index on t_test (doc_id). There is others index too.
>
> When I send this request, I must wait for about 45 sec. before the results
> appears.
> The server is a BI-PII 266, and there is about no activity on the database
> neither on the server.
>
> When I was using this request under MS-SQLServer (v6), the wait time was
> about nothing.
>
> What's wrong ?

A few questions:
1) Which version of postgres are you using?
2) Have you 'VACUUM ANALYZE t_test' and 'VACUUM ANALYZE doc' yet?

Try #2, it should help you quite a bit.

-- Dave

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