Re: Effective Cache Size - Mailing list pgsql-performance

From Manfred Koizar
Subject Re: Effective Cache Size
Date
Msg-id a9j3gvgg2r7idrmfu7st9h8odc7pogq2lj@4ax.com
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In response to Effective Cache Size  (Howard Oblowitz <HowardO@LEWIS-STORES.com>)
List pgsql-performance
On Tue, 1 Jul 2003 15:50:14 +0200 , Howard Oblowitz
<HowardO@LEWIS-STORES.com> wrote:
>What then will be the effect of setting this too high?

The planner might choose an index scan where a sequential scan would
be faster.

>And too low?

The planner might choose a sequential scan where an index scan would
be faster.

>How does it impact on other applications eg Java ?

It doesn't -- at least not directly.  (There could be very subtle
effects when Postgres does a sequential scan over a large relation
thus pushing everything else out of the cache, where an index scan
would have read only a small number of pages.  Or when a large index
scan turns your machine from CPU bound to I/O bound.)

Servus
 Manfred

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