Date: Sun, 12 May 2002 12:49:35 -0500 (CDT)
From: Brian McCane <bmccane@mccons.net>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-admin <pgsql-admin@postgresql.org>
Subject: Re: VACUUM FULL 
In-Reply-To: <178.1021219490@sss.pgh.pa.us>
Message-ID: <20020512124637.E81191-100000@fw.mccons.net>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


Tom,
	I was going to do a pg_ctl stop/start cycle to try to fix the
error, however....

What do I need to do to debug?  I am on FreeBSD 5.0.  I assume I can use
GDB to connect to a running backend, but have not done any serious
debugging in gdb for 4-5 years.  If it is too ugly, I might consider
allowing someone into the machine, but it doesn't make me excited to
contemplate it.

- brian


On Sun, 12 May 2002, Tom Lane wrote:

>
> Brian McCane <bmccane@mccons.net> writes:
> > Okay, now I am a little scared.  Before I started rebuilding indexes, I
> > decided to do the VACUUM FULL thing on all of my tables.  On my two most
> > referenced tables I am getting:
>
> > ERROR:  No one parent tuple was found
>
> Oh, that's interesting.  We've gotten sporadic reports of that error
> message but no one's ever submitted a reproducible case.  Don't suppose
> you want to trace through VACUUM FULL with a debugger (or let someone
> else do so) to see why it's getting confused?
>
> FWIW, I don't think you need fear data loss.  VACUUM FULL has some, um,
> quite baroque code to deal with moving update chains as a unit, and it's
> just reporting that it couldn't figure out how to move what looked like
> a tuple chain.
>
> AFAIK this situation can only occur when there are open transactions
> that can still see some already-replaced tuple.  So the error would
> probably go away if you closed all your open transactions.
>
> 			regards, tom lane
>
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