Re: Possible bug in vacuum redo

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>
Cc: Vadim Mikheev <vmikheev(at)sectorbase(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Possible bug in vacuum redo
Date: 2001-12-24 01:28:04
Message-ID: 5781.1009157284@sss.pgh.pa.us
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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...

regards, tom lane

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