From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Merlin Moncure <mmoncure@gmail.com>
Cc: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: Sok Ann Yap <sokann@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: reducing random_page_cost from 4 to 2 to force index scan
Date: Fri, 13 May 2011 15:20:37 -0400
Message-ID: <2823.1305314437@sss.pgh.pa.us> (raw)
In-Reply-To: <BANLkTik6OaVkJGEjs5--vcynUE36mWbzbg@mail.gmail.com>
References: <BANLkTikZhYc+h1=YDJfXwZEZc1tN3_VwCg@mail.gmail.com>
<4DB6F4BB020000250003CEB9@gw.wicourts.gov>
<BANLkTindB68ogMg8zrR7GrYEV+mQQddj0A@mail.gmail.com>
<BANLkTik6OaVkJGEjs5--vcynUE36mWbzbg@mail.gmail.com>
Robert Haas <robertmhaas@gmail.com> writes:
> On Tue, Apr 26, 2011 at 9:04 PM, Merlin Moncure <mmoncure@gmail.com> wrote:
>> The very first thing to check is effective_cache_size and to set it to
>> a reasonable value.
> Actually, effective_cache_size has no impact on costing except when
> planning a nested loop with inner index scan. So, a query against a
> single table can never benefit from changing that setting.
That's flat out wrong. It does affect the cost estimate for plain
indexscan (and bitmap indexscan) plans.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, robertmhaas@gmail.com, mmoncure@gmail.com, Kevin.Grittner@wicourts.gov, sokann@gmail.com
Subject: Re: reducing random_page_cost from 4 to 2 to force index scan
In-Reply-To: <2823.1305314437@sss.pgh.pa.us>
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