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Re: Unnecessary scan on a partial index slows down query dramatically

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Jimmy Choi" <yhjchoi(at)gmail(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Unnecessary scan on a partial index slows down query dramatically
Date: 2008-04-25 16:13:55
Message-ID: 20727.1209140035@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-general
"Jimmy Choi" <yhjchoi(at)gmail(dot)com> writes:
> A simple query is executing much slower than expected. When looking at
> the query plan, I see a bitmap index scan on a partial index that does
> not have any associated index condition. How could that happen?

Easily --- it thinks that the partial index predicate is useful in
itself.

> "vacuum analyze" doesn't solve the problem. I'm running 8.1.5.

choose_bitmap_and was rewritten (again) in 8.1.9.  Try a newer
version.

http://archives.postgresql.org/pgsql-committers/2007-04/msg00233.php

			regards, tom lane

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