From: Craig A. James <cjames@modgraph-usa.com>
To: Michael Stone <mstone+postgres@mathom.us>
To: pgsql-performance@postgresql.org
Subject: Re: Forcing using index instead of sequential scan?
Date: Sun, 23 Jul 2006 07:03:59 -0700
Message-ID: <44C381CF.4050800@modgraph-usa.com> (raw)
In-Reply-To: <20060723110724.GU8069@mathom.us>
References: <D012B9600FFB984AB18C0D53C475A4A081F51B@E03MVZ3-UKDY.domain1.systemhost.net>
<26827.1153585341@sss.pgh.pa.us>
<44C25FDD.8070003@modgraph-usa.com>
<20060723110724.GU8069@mathom.us>
Michael Stone wrote:
> On Sat, Jul 22, 2006 at 10:26:53AM -0700, Craig A. James wrote:
>> This causes massive file-system activity and flushes all files that
>> the kernel has cached. If you run this between each Postgres test
>> (let it run for a couple minutes), it gives you an apples-to-apples
>> comparison between successive benchmarks, and eliminates the effects
>> of caching.
>
> Assuming a system with small ram or an unusually large system
> installation. Unmounting is a much more realiable mechanism.
Indeed, but it only works if you can. For example, in my small-ish installation, my WAL and system tables are mounted on the root disk. Or someone might not have super-user access.
Craig
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To: pgsql-performance@postgresql.org
Cc: cjames@modgraph-usa.com, mstone+postgres@mathom.us
Subject: Re: Forcing using index instead of sequential scan?
In-Reply-To: <44C381CF.4050800@modgraph-usa.com>
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