Re: Temporary tables and disk activity

From: Phil Endecott <spam_from_postgresql_general(at)chezphil(dot)org>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: Temporary tables and disk activity
Date: 2004-12-13 00:46:24
Message-ID: 41BCE660.1030108@chezphil.org
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Tom Lane wrote:
> They [temporary tables]
> will be written out from PG's internal buffers, but IIRC they will
> never be fsync'd, and they definitely aren't WAL-logged. (These
> statements hold true in 8.0, but not sure how far back.)
>
> In principle, therefore, the kernel could hold temp table data in its
> own disk buffers and never write it out to disk until the file is
> deleted. In practice, of course, the kernel doesn't know the data is
> transient and will probably push it out whenever it has nothing else to
> do.

That makes sense. I suspect that I am seeing writes every 5 seconds,
which looks like bdflush / update.

But my connections normally only last for a second at most. In this
case, surely the table would normally have been deleted before the
kernel decided to write anything. This is with 7.4.2 on linux 2.4.26.
Does anyone have any experience with this type of situation? Is there
any kernel-tweaking I can play with?

Regards,

Phil.

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