Re: vacuum, dead rows, usual solutions didn't help

From: Lars Heidieker <lars(at)heidieker(dot)de>
To: Gábor Farkas <gabor(at)nekomancer(dot)net>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: vacuum, dead rows, usual solutions didn't help
Date: 2008-01-10 11:05:59
Message-ID: 14573F45-4B72-43DD-884F-A704A2A73C38@heidieker.de
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On 10 Jan 2008, at 11:18, Gábor Farkas wrote:

> Simon Riggs wrote:
>>> also, even if it is wrong, can an 'idle-in-transaction'
>>> connection that was opened today block the vacuuming of rows that
>>> were deleted yesterday?
>> Yes, if the rows were deleted after the connection started.
>
> to avoid any potential misunderstandings, i will summarize the
> situation:
>
> 1. the vacuum-cronjob refuses to remove dead rows since 1.jan.2008.
>
> 2. i know that no postgres-process is older than 7.jan.2008. (from
> "ps aux | grep postgres", and except the postgres-system-processes)
>
> how can this happen?
>
>

To my understanding the question how old the processes are is only
partially of interest,
if a process touches those rows in a transaction just before the
vacuum runs, it can't remove those rows.
So all you need to get in this situation is a transaction that
touches the rows in a transaction and
keeps the transaction alive before vacuum runs.

- --

Viele Grüße,
Lars Heidieker

lars(at)heidieker(dot)de
http://paradoxon.info

- ------------------------------------

Mystische Erklärungen:
Die mystischen Erklärungen gelten für tief;
die Wahrheit ist, dass sie noch nicht einmal oberflächlich sind.

-- Friedrich Nietzsche
[ Die Fröhliche Wissenschaft Buch 3, 126 ]

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