Re: Nasty VACUUM/bgwriter/segmentation bug

From: "Florian G(dot) Pflug" <fgp(at)phlo(dot)org>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Nasty VACUUM/bgwriter/segmentation bug
Date: 2006-11-19 20:28:49
Message-ID: 4560BE81.6030907@phlo.org
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Heikki Linnakangas wrote:
> Florian G. Pflug wrote:
>> Joshua D. Drake wrote:
>>> On Sun, 2006-11-19 at 11:28 -0800, Josh Berkus wrote:
>>>> Tom,
>>>>> Let's go with the easy fix. With regular 1GB segment size, having a
>>>>> few
>>>>> empty files in the data directory isn't going to hurt anyone.
>>>> No, but it will confuse DBAs ("What the heck are all these 0B
>>>> files?"). Maybe we should add code to VACUUM to look for these
>>>> empty file segments and unlink them if they haven't been touched in
>>>> a while (say, a day?).
>>>
>>> I don't buy this argument. A smart DBA isn't going to do any such thing.
>>> If you go around deleting unknown files you deserve everything you get.
>>> Especially if you are in the middle of a PostgreSQL cluster tree.
>>
>> Couldn't some application trigger this problem regularly (Say, once a
>> day while
>> importing new data), and therefore create an ever increasing number of
>> empty
>> files that you can't get rid of without backup,reinit and restore?
>
> No, the old empty files would get reused if the relation grows again.
> And they would get deleted if you truncate or drop the relation.
Ah, sorry, I had misunderstood that point. I believed that a new
segment would be created when the relation grows again, and the
empty file would linger around forever...

Thanks for your explaination
greetings, Florian Pflug

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