Re: [HACKERS] HOT WIP Patch - version 2

Tom Lane wrote:
> Bruce Momjian <bruce@momjian.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@momjian.us>          http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

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