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Re: Forcing using index instead of sequential scan?

From: "Craig A(dot) James" <cjames(at)modgraph-usa(dot)com>
To: Michael Stone <mstone+postgres(at)mathom(dot)us>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Forcing using index instead of sequential scan?
Date: 2006-07-23 14:03:59
Message-ID: 44C381CF.4050800@modgraph-usa.com (view raw or flat)
Thread:
Lists: pgsql-performance
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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