From: Tom Lane <tgl@sss.pgh.pa.us>
To: arnaulist@andromeiberica.com
Cc: pgsql-performance@postgresql.org
Subject: Re: Query on postgresql 7.4.2 not using index
Date: Tue, 25 Apr 2006 11:55:36 -0400
Message-ID: <19861.1145980536@sss.pgh.pa.us> (raw)
In-Reply-To: <444E44A2.6030703@andromeiberica.com>
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<3c1395330604250634r6f215ceame157f3dd5f5f4fa3@mail.gmail.com>
<444E28ED.3090900@andromeiberica.com>
<19483.1145978579@sss.pgh.pa.us>
<444E44A2.6030703@andromeiberica.com>
Arnau <arnaulist@andromeiberica.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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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, arnaulist@andromeiberica.com
Subject: Re: Query on postgresql 7.4.2 not using index
In-Reply-To: <19861.1145980536@sss.pgh.pa.us>
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