Re: TPC-R benchmarks

From: George Essig <george_essig(at)yahoo(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Oleg Lebedev <oleg(dot)lebedev(at)waterford(dot)org>, Mary Edie Meredith <maryedie(at)osdl(dot)org>, Jenny Zhang <jenny(at)osdl(dot)org>, pgsql-performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: TPC-R benchmarks
Date: 2003-10-01 16:55:53
Message-ID: 20031001165553.22593.qmail@web80215.mail.yahoo.com
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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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