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

"Jimmy Choi" <yhjchoi@gmail.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