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Re: Query on postgresql 7.4.2 not using index

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: arnaulist(at)andromeiberica(dot)com
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Query on postgresql 7.4.2 not using index
Date: 2006-04-25 15:55:36
Message-ID: 19861.1145980536@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Arnau <arnaulist(at)andromeiberica(dot)com> writes:
> I have done the same tests on 8.1.0.

Bitmap scans are a totally different animal that doesn't exist in 7.4.
A plain indexscan, such as 7.4 knows about, is generally not effective
for fetching more than a percent or two of the table.  The crossover
point for a bitmap scan is much higher (don't know exactly, but probably
something like 30-50%).

			regards, tom lane

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