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Re: Possible bug in vacuum redo

From: Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
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 01:04:47
Message-ID: 3C267F2F.99D6A78E@tpf.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackers
Tom Lane wrote:
> 
> Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp> writes:
> > I don't think it's preferable either. However there's
> > no problem unless there's an application which handle
> > the tuples containing the t_ctid link.
> 
> What about READ COMMITTED mode?  EvalPlanQual uses the t_ctid field
> to find the updated version of the row.

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.

regards,
Hiroshi Inoue

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