Re: Question about caching on full table scans - Mailing list pgsql-performance

From Jeff Janes
Subject Re: Question about caching on full table scans
Date
Msg-id CAMkU=1xZ822+Z06ZTFA8T+K8m1k4jh4tXvZuuv_cn=o+C_eTfA@mail.gmail.com
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In response to Re: Question about caching on full table scans  (Markus Innerebner <markus.innerebner@inf.unibz.it>)
List pgsql-performance
On Thu, Aug 30, 2012 at 10:34 AM, Markus Innerebner
<markus.innerebner@inf.unibz.it> wrote:
>
> > To flush the filesystem cache (from Linux 2.6.16 on), use
> > sync; echo 3 > /proc/sys/vm/drop_caches
>
>
> I started to do that , and
> yes, this solves my problem!!
>
> I assume that deleting file system cache implies that also postgres cache is
> deleted, isn't it ?


No, the postgres-managed cache is not cleared by doing that.  In order
to get rid of both layers of caching, you should restart the postgres
server and then do the drop_caches.

Cheers,

Jeff


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