Re: [HACKERS] HOT WIP Patch - version 2

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, pgsql-patches(at)postgresql(dot)org
Subject: Re: [HACKERS] HOT WIP Patch - version 2
Date: 2007-02-20 14:50:40
Message-ID: 26769.1171983040@sss.pgh.pa.us
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Bruce Momjian <bruce(at)momjian(dot)us> writes:
> Pavan Deolasee wrote:
>> When following a HOT-update chain from the index fetch, if we notice that
>> the root tuple is dead and it is HOT-updated, we try to prune the chain to
>> the smallest possible length. To do that, the share lock is upgraded to an
>> exclusive lock and the tuple chain is followed till we find a
>> live/recently-dead
>> tuple. At that point, the root t_ctid is made point to that tuple. In order

> I assume you meant recently-dead here, rather than live/recently-dead,
> because we aren't going to change live ctids, right?

"Recently dead" means "still live to somebody", so those tids better not
change either. But I don't think that's what he meant. I'm more
worried about the deadlock possibilities inherent in trying to upgrade a
buffer lock. We do not have deadlock detection for LWLocks.

regards, tom lane

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