Message-ID: <1219536553.48b0a6a9c6ea2@imp.free.fr>
Date: Sun, 24 Aug 2008 02:09:13 +0200
From: tls.wydd@free.fr
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: DiezelMax <max@nts.biz.ua>, pgsql-performance@postgresql.org
Subject: Re: Large number of tables slow insert
References: <1775c5ea0808221841u746862e3h1b721ea82fdb7794@mail.gmail.com>
	<48AFE6BB.6040400@nts.biz.ua>
	<1219520134.48b0668645ce4@imp.free.fr>
	<dcc563d10808231649k7cc447cwbb8228f2b97c42fa@mail.gmail.com>
In-Reply-To: <dcc563d10808231649k7cc447cwbb8228f2b97c42fa@mail.gmail.com>
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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. 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 ?

I cannot do test this weekend because I do not have access to the machine but I
will try on monday some tests.

Thanks for your answers thought

Selon Scott Marlowe <scott.marlowe@gmail.com>:

> On Sat, Aug 23, 2008 at 1:35 PM,  <tls.wydd@free.fr> wrote:
> > Actually, I've got another test system with only few sensors (thus few
> tables)
> > and it's working well (<10ms insert) with all the indexes.
> > I know it's slowing down my performance but I need them to interogate the
> big
> > tables (each one can reach millions rows with time) really fast.
>
> It's quite likely that on the smaller system the indexes all fit into
> memory and only require writes, while on the bigger system they are
> too large and have to be read from disk first, then written out.
>
> A useful solution is to remove most of the indexes on the main server,
> and set up a slony slave with the extra indexes on it to handle the
> reporting queries.
>
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