Re: 8.1 index corruption woes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 8.1 index corruption woes
Date: 2008-07-08 01:28:17
Message-ID: 27175.1215480497@sss.pgh.pa.us
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Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Tom Lane wrote:
>> Another point to keep in mind, if you are trying to analyze files
>> belonging to a live database, is that what you can see in the filesystem
>> may not be the "current" contents of every page. For typical access
>> patterns it'd be unsurprising for the visible index pages to lag behind
>> those of the heap, since they'd be "hotter" and tend to stay in shared
>> buffers longer.

> Hmm, I think the files come from a PITR slave that's not online. I'll
> ask to be sure.

8.1 didn't have restartpoint code, and of course bgwriter isn't running;
so I believe filesystem pages on a PITR slave could be arbitrarily far
out of date if the corresponding shared buffer got touched regularly.
Try doing the analysis on the master immediately after a CHECKPOINT
command.

regards, tom lane

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