| 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 |
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| 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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