From: Andrus <kobruleht2@hot.ee>
To: pgsql-performance@postgresql.org
Subject: Using index for IS NULL query
Date: Tue, 11 Nov 2008 21:55:55 +0200
Message-ID: <gfcprb$m40$1@news.hub.org> (raw)
Index is not used for
is null
condition:
create index makse_dokumnr_idx on makse(dokumnr);
explain select
sum( summa)
from MAKSE
where dokumnr is null
"Aggregate (cost=131927.95..131927.96 rows=1 width=10)"
" -> Seq Scan on makse (cost=0.00..131927.94 rows=1 width=10)"
" Filter: (dokumnr IS NULL)"
Table makse contains 1200000 rows and about 800 rows with dokumnr is null so
using index is much faster that seq scan.
How to fix ?
Andrus.
"PostgreSQL 8.1.4 on i686-pc-linux-gnu, compiled by GCC
i686-pc-linux-gnu-gcc (GCC) 3.4.6 (Gentoo 3.4.6-r1, ssp-3.4.5-1.0,
pie-8.7.9)"
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To: pgsql-performance@postgresql.org
Cc: kobruleht2@hot.ee
Subject: Re: Using index for IS NULL query
In-Reply-To: <gfcprb$m40$1@news.hub.org>
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