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Re: [HACKERS] HOT WIP Patch - version 2

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(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 14:51:50
Message-ID: 200702201451.l1KEppu22326@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Tom Lane wrote:
> 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.

I am guessing he is going to have to release the lock, then ask for an
exclusive one.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>          http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +

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