Re: TPC-R benchmarks - Mailing list pgsql-performance

From George Essig
Subject Re: TPC-R benchmarks
Date
Msg-id 20031001165553.22593.qmail@web80215.mail.yahoo.com
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In response to TPC-R benchmarks  (Oleg Lebedev <oleg.lebedev@waterford.org>)
List pgsql-performance
Tom Lane wrote:

> When benchmarking with data sets considerably larger than available
> buffer cache, I rather doubt that small random_page_cost would be a
> good idea.  Still, you might as well experiment to see.

From experience, I know the difference in response time can be huge when postgres incorrectly
chooses a sequential scan over an index scan.  In practice, do people experience as great a
difference when postgres incorrectly chooses an index scan over a sequential scan?  My intuition
is that the speed difference is a lot less for incorrectly choosing an index scan.  If this is the
case, it would be safer to chose a small value for random_page_cost.

George Essig

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