Re: [HACKERS] HOT WIP Patch - version 2

Pavan Deolasee wrote:
> On 2/20/07, Bruce Momjian  wrote:
> >
> > 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?
> 
> 
> No, I meant live or recently-dead (in fact, anything  other than
> HEAPTUPLE_DEAD
> or HEAPTUPLE_DEAD_CHAIN).
> 
> We are not changing the tids here, but only pruning the HOT-update chain.
> After pruning, the root->t_ctid points to the oldest tuple that might be
> visible to any backend. The live tuples are still identified by their
> original tid and index reachable from the root tuple.

I am confused.  Where is the root->t_ctid stored?

-- 
  Bruce Momjian            http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

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