From: | Manfred Koizar <mkoi-pg(at)aon(dot)at> |
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To: | Howard Oblowitz <HowardO(at)LEWIS-STORES(dot)com> |
Cc: | "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Effective Cache Size |
Date: | 2003-07-01 18:22:13 |
Message-ID: | a9j3gvgg2r7idrmfu7st9h8odc7pogq2lj@4ax.com |
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Lists: | pgsql-performance |
On Tue, 1 Jul 2003 15:50:14 +0200 , Howard Oblowitz
<HowardO(at)LEWIS-STORES(dot)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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