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Message-ID: <dcc563d10808231725q13556r435d68939b0e9b71@mail.gmail.com>
Date: Sat, 23 Aug 2008 18:25:52 -0600
From: "Scott Marlowe" <scott.marlowe@gmail.com>
To: tls.wydd@free.fr
Subject: Re: Large number of tables slow insert
Cc: DiezelMax <max@nts.biz.ua>, pgsql-performance@postgresql.org
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References: <1775c5ea0808221841u746862e3h1b721ea82fdb7794@mail.gmail.com>
	<48AFE6BB.6040400@nts.biz.ua> <1219520134.48b0668645ce4@imp.free.fr>
	<dcc563d10808231649k7cc447cwbb8228f2b97c42fa@mail.gmail.com>
	<1219536553.48b0a6a9c6ea2@imp.free.fr>

On Sat, Aug 23, 2008 at 6:09 PM,  <tls.wydd@free.fr> wrote:
> On this smaller test, the indexes are over the allowed memory size (I've got
> over 400.000 readings per sensor) so they are mostly written in disk.

They're always written to disk.  Just sometimes they're not read.
Note that the OS caches files as well as pgsql, and I'm not sure what
you mean by "allowed memory size" but only the shared_buffers would
hold onto something after it's been operated on.  work_mem won't.

> And on the
> big test, I had small indexes (< page_size) because I only had about 5-10 rows
> per table, thus it was 3000*8kb = 24mb which is lower than the allowed memory.

> btw which is the conf parameter that contains the previously read indexes ?

Not sure what you're asking.  It's all automatic as far as OS and
postgresql caching goes.