many 'OR' in WHERE-condition

From: "A(dot) Kretschmer" <andreas(dot)kretschmer(at)schollglas(dot)com>
To: pgsql-sql(at)postgresql(dot)org
Subject: many 'OR' in WHERE-condition
Date: 2007-04-20 05:13:42
Message-ID: 20070420051341.GA15322@a-kretschmer.de
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-sql

Hello,

a friend of mine has got a problem:

in a SELECT with a condition 'WHERE foo IN (1,2,3,4,...)' with a large
list within. The optimizer choose a rewrite to many OR's and a bitmap
index scan on the index, no problem, fast.

But if the list increase the planner choose an seq-scan. The amount of
values in the list is about 200 and the table has about 250.000 rows.

How can we avoid the seq-scan?

Andreas, thx in advance.
--
Andreas Kretschmer
Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header)
GnuPG-ID: 0x3FFF606C, privat 0x7F4584DA http://wwwkeys.de.pgp.net

Responses

Browse pgsql-sql by date

  From Date Subject
Next Message Dmitry Turin 2007-04-20 09:08:19 Re: We all are looped on Internet: request + transport = invariant
Previous Message Phillip Smith 2007-04-19 22:52:00 Re: slowness when subselect uses DISTINCT