To: pginfo <pginfo@t1.unisoftbg.com>
Cc: Richard_D_Levine@raytheon.com,
	Michael Glaesemann <grzm@myrealbox.com>, pgsql-sql@postgresql.org
Subject: Re: pg primary key bug? 
In-reply-to: <421AFC7F.406@t1.unisoftbg.com> 
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Comments: In-reply-to pginfo <pginfo@t1.unisoftbg.com>
	message dated "Tue, 22 Feb 2005 10:33:51 +0100"
Date: Tue, 22 Feb 2005 11:37:30 -0500
Message-ID: <10243.1109090250@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>

pginfo <pginfo@t1.unisoftbg.com> writes:
> You idea was that we have "vacuum full" + update or select for update in 
> the same time.
> I think it is not the case, because we start vacuum full at 1:00 AM and 
> no one is working in this time.

Hmm.  AFAICT the duplicate row copies could only be produced by vacuum
full, so that's certainly part of the issue.  But if vacuum full in
isolation were broken, we'd surely know it; so there must be some other
contributing factor involved that your setup is exercising but other
people are (mostly) not doing.

I agree with the plan to use plain vacuum for awhile and see if that
makes the problem go away.  I think it would have to, but maybe I'm
all wet about that.

In the meantime I would suggest seeing if you can distill your
application down into a test case that other people can run to reproduce
the problem.  It doesn't matter if the test doesn't make the bug happen
very often, but we have to see the problem happening before we have much
hope of fixing it.

> Will vacuum full generate this problem if we have locked table in this 
> time? (It is possible to have locked table in theory)

No, that's hardly likely.  vacuum full deals with locks all the time.

> Can you describe more detailed the idea of  problem with "vacuum full" + 
> "update" and can some one make patch if this problem exists in theory 
> (if I  understand you right)?

I have no idea what the actual failure mechanism might be.

			regards, tom lane