Subject: Forcing more agressive index scans for BITMAP AND
From: Ow Mun Heng <Ow.Mun.Heng@wdc.com>
To: pgsql-performance@postgresql.org
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Date: Mon, 07 Apr 2008 16:15:51 +0800
Message-Id: <1207556151.19677.2.camel@neuromancer.home.net>
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just wondering if there's a special tweak i can do to force more usage
of indexes to do BITMAP ands?

I have a table like

A int
B int
C int
D int
E int
F int
g int

where A/B/C/D/E are indexes

There's ~20millions rows in the table.

Query are something like this.

select * from table 
where A=X
and B = Y
and C = Z
and D = AA
and E = BB

the query plan will only pick 2 indexes to do the bitmap.
I'm not sure how to tweak the config for it to use more indexes.

Box is a celeron 1.7 w/ 768MB ram with shared buffers at 250MB and
effective cache size 350MB