Message-ID: <4CB4602A.3040800@2ndquadrant.com>
Date: Tue, 12 Oct 2010 09:18:34 -0400
From: Greg Smith <greg@2ndquadrant.com>
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To: Jon Nelson <jnelson+pgsql@jamponi.net>
CC: mladen.gogala@vmsinfo.com, "david@lang.hm" <david@lang.hm>,
	Craig Ringer <craig@postnewspapers.com.au>,
	Vitalii Tymchyshyn <tivv00@gmail.com>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Slow count(*) again...
References: <201010091626.18636.neil.whelchel@gmail.com>
	<AANLkTimayTM__hHu9RoiLaNhzfpNY6Vo5y4OkbX_sV=o@mail.gmail.com>
	<4CB34D69.6060108@emolecules.com> <4CB4149D.8030803@gmail.com>
	<4CB41902.1020503@postnewspapers.com.au>
	<alpine.DEB.2.00.1010120118030.21889@asgard.lang.hm>
	<4CB4542E.5010406@vmsinfo.com>
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Jon Nelson wrote:
> Is there a command to tell postgresql to drop/clear/reset it's buffer_cache?
>   

No.  Usually the sequence used to remove all cached data from RAM before 
a benchmark is:

pg_ctl stop
sync
echo 3 > /proc/sys/vm/drop_caches
pg_ctl start

-- 
Greg Smith, 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services and Support  www.2ndQuadrant.us
Author, "PostgreSQL 9.0 High Performance"    Pre-ordering at:
https://www.packtpub.com/postgresql-9-0-high-performance/book