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Re: Duplicate values found when reindexing unique index

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Mason Hale <masonhale(at)gmail(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: Duplicate values found when reindexing unique index
Date: 2007-12-31 17:47:59
Message-ID: 1199123279.9558.185.camel@ebony.site (view raw or flat)
Thread:
Lists: pgsql-bugs
On Mon, 2007-12-31 at 12:33 -0500, Tom Lane wrote:
> Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > On Mon, 2007-12-31 at 11:53 -0500, Tom Lane wrote:
> >> The state of the ...0058 file might be explained by the theory that
> >> you'd archived it a bit too late (after the first page had been
> >> overwritten with newer WAL data), 
> 
> > The interlock with .ready and .done should prevent reuse of a file. So
> > the only way this could happen is if the archive_command queued a
> > request to copy, rather than performing the copy immediately.
> > So I was going to say "thats not possible", but perhaps rsync might
> > become confused by the file renaming mechanism we use? 
> 
> Actually, the other problem with that theory is that the slave swallowed
> the file without complaint.  

No, it barfed. Mason showed us a recovery script, so it came from the
slave.

> Since the WAL reader code does check that
> the page header contains the expected address, this seems to imply that
> what the slave saw must have had 422/58 in it, not the 423/C1 we see
> now.  So what needs to be explained is why what Mason is looking at now
> is different from what the slave saw ten days ago.

So the slave did see a problem ten days ago, though I take your point
that the problem we see now may not be the as it was back then.

-- 
  Simon Riggs
  2ndQuadrant  http://www.2ndQuadrant.com


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