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From: Andrus <kobruleht2@hot.ee>
To: Vladimir Sitnikov <sitnikov.vladimir@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Increasing select max(datecol) from bilkaib where datecol<=date'2008-11-01' and (cr='00' or db='00') speed
Date: Wed, 12 Nov 2008 21:44:38 +0200
Message-ID: <498EDF1308A1409E9CE994C83A345BA3@andrusnotebook> (raw)
In-Reply-To: <1d709ecc0811121126k4558db13m88c959188c3a9c0f@mail.gmail.com>
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	<alpine.DEB.1.10.0811121730500.4666@aragorn.flymine.org>
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	<1d709ecc0811121126k4558db13m88c959188c3a9c0f@mail.gmail.com>

Vladimir,

>I am afraid PostgreSQL is not smart enough to rewrite query with "or" into 
>two separate index scans. There is no way to improve the query 
>significantly without rewriting it.
>Note:  for this case indices on (datecol), (cr) and (db) are not very 
>helpful.

Thank you very much.
I added you indexes to db and re-write query.
Now it runs fast.

Andrus.




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