Re: Forcing using index instead of sequential scan?

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От Craig A. James
Тема Re: Forcing using index instead of sequential scan?
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Msg-id 44C381CF.4050800@modgraph-usa.com
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Ответ на Re: Forcing using index instead of sequential scan?  (Michael Stone <mstone+postgres@mathom.us>)
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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
onthe root disk.  Or someone might not have super-user access. 

Craig

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