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Re: Possible bug in vacuum redo

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>, Vadim Mikheev <vmikheev(at)sectorbase(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Possible bug in vacuum redo
Date: 2002-01-03 05:53:54
Message-ID: 200201030553.g035rsj14062@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane wrote:
> Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp> writes:
> > In READ COMMITTED mode, an app searches valid tuples first
> > using the snapshot taken when the query started. It never
> > searches already updated(to newer ones) and committed tuples
> > at the point when the query started. Essentially t_ctid is
> > only needed by the concurrently running backends.
> 
> [ thinks for awhile ]  I see: you're saying that t_ctid is only
> used by transactions that are concurrent with the deleting transaction,
> so if there's a database crash there's no need to restore t_ctid.
> 
> Probably true, but still mighty ugly.
> 
> Meanwhile, I guess I gotta look elsewhere for a theory to explain
> those reports of duplicate rows.  Oh well...

Can someone document this in the sources somewhere?  I am not sure how
to do it.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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