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count(*) slow on large tables - Mailing list pgsql-performance

From Dror Matalon
Subject count(*) slow on large tables
Date
Msg-id 20031002191547.GZ87525@rlx11.zapatec.com
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Responses Re: count(*) slow on large tables  (Bruno Wolff III <bruno@wolff.to>)
Re: count(*) slow on large tables  (Tomasz Myrta <jasiek@klaster.net>)
List pgsql-performance
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Hi,

I have a somewhat large table, 3 million rows, 1 Gig on disk,  and growing. Doing a
count(*) takes around 40 seconds.

Looks like the count(*) fetches the table from disk and goes through it.
Made me wonder, why the optimizer doesn't just choose the smallest index
which in my case is around 60 Megs and goes through it, which it could
do in a fraction of the time.

Dror


--
Dror Matalon
Zapatec Inc
1700 MLK Way
Berkeley, CA 94709
http://www.zapatec.com

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