Re: The suppress_redundant_updates_trigger() works incorrectly

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andrew Dunstan <andrew(at)dunslane(dot)net>
Cc: KaiGai Kohei <kaigai(at)ak(dot)jp(dot)nec(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: The suppress_redundant_updates_trigger() works incorrectly
Date: 2008-11-05 18:10:35
Message-ID: 434.1225908635@sss.pgh.pa.us
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Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> The attached patch sets the OID to InvalidOid for the duration of the
> memcmp if the HEAP_HASOID flag is set, and restores it afterwards.

This method is utterly, utterly unacceptable; you're probably trashing
the contents of a disk buffer there. Even assuming that there's zero
risk of a failure between the set and the restore, what if someone is in
process of writing the buffer to disk? Or even just examining the old
tuple?

regards, tom lane

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