Re: select on 22 GB table causes "An I/O error occured while sending to the backend." exception

From: Matthew Wakeling <matthew(at)flymine(dot)org>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: select on 22 GB table causes "An I/O error occured while sending to the backend." exception
Date: 2008-08-28 20:09:24
Message-ID: alpine.DEB.1.10.0808282104410.4454@aragorn.flymine.org
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On Thu, 28 Aug 2008, david(at)lang(dot)hm wrote:
> I just asked on the kernel mailing list and Alan Cox responded.
>
> he is saying that you are correct, it only allocates against the total
> available, it doesn't actually allocate ram.

That was remarkably graceful of you. Yes, operating systems have worked
that way for decades - it's the beauty of copy-on-write.

> but you do need to allocate more swap as the total memory 'used' can be
> significantly higher that with overcommit on.

Yes, that's right.

Matthew

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