Re: page is uninitialized --- fixing

From: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Brad Nicholson <bnichols(at)ca(dot)afilias(dot)info>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: page is uninitialized --- fixing
Date: 2008-03-30 09:46:09
Message-ID: 47EF6161.7030201@kaltenbrunner.cc
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Tom Lane wrote:

> This is not entirely out of the question, because of the designed-in
> property that a freshly initialized page is only inserted into by
> the backend that got it --- no one else will know there is any
> free space in it until VACUUM first passes over it. So if there
> are a lot of different sessions writing into this table you don't
> need to assume more than about one tuple per page. Still, it's
> kinda hard to believe that the first two backends could remain stuck
> for so long as to let ~800 other insertions happen.

depending on how the multipathing and recovery works on that particular
SAN/OS combination it might very well be that some processes are getting
their IO hold much longer than some other processes.
Maybe the first two backends had IO in-flight and the OS needed time to
requeue/resend those after the SAN recovered and "new" backends were
able to do IO immediately ?

Stefan

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