Re: tuptoaster.c must *not* use SnapshotAny

From: "Command Prompt, Inc(dot)" <pgsql-hackers(at)commandprompt(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Jan Wieck <JanWieck(at)Yahoo(dot)com>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: tuptoaster.c must *not* use SnapshotAny
Date: 2002-01-16 17:46:32
Message-ID: Pine.LNX.4.30.0201160944480.30961-100000@commandprompt.com
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Josh Drake here: Although I know that development has pretty much ceased
on the 7.1 series. This bug, is potentially very serious for those who
have the problem.

The last time this came up (that I can find) is in August of 2001, so the
bug is not frequent that we are aware of. However, as it appears the fix
is simple should we apply a 7.1.3.1 or 7.1.4 that fixes this issue?

J

> On Tue, 15 Jan 2002, Tom Lane wrote:

> The tuple toaster currently fetches toast-table rows using SnapshotAny.
> This is quite uncool, because it will in fact find *any* row. Including
> dead rows resulting from an aborted (or, in 7.2, still-in-progress)
> VACUUM.
>
> I believe this is the explanation for a problem report I'm currently
> chasing from Joshua Drake:
>
> digivision2=# select * from change_log;
> ERROR: chunk 1 for toast value 3388774 appears multiple times
>
> (there are some thousands of rows with similar problems)
>
> I suggest SnapshotSelf instead. Comments anyone?
>
> regards, tom lane
>
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