Skip site navigation (1) Skip section navigation (2)

Re: COUNT(*) again (was Re: [HACKERS] Index/Function organized

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Hannu Krosing <hannu(at)tm(dot)ee>,Christopher Browne <cbbrowne(at)libertyrms(dot)info>,pgsql-performance(at)postgresql(dot)org,"pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: COUNT(*) again (was Re: [HACKERS] Index/Function organized
Date: 2003-10-05 13:36:40
Message-ID: 200310051336.h95Daee20397@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Tom Lane wrote:
> >> I think that's not happening, conditionally or otherwise.  The atomicity
> >> problems alone are sufficient reason why not, even before you look at
> >> the performance issues.
> 
> > What are the atomicity problems of adding a create/expire xid to the
> > index tuples?
> 
> You can't update a tuple's status in just one place ... you have to
> update the copies in the indexes too.

But we don't update the tuple status for a commit, we just mark the xid
as committed.  We do have lazy status bits that prevent later lookups in
pg_clog, but we have those in the index already also.

What am I missing?

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

In response to

pgsql-performance by date

Next:From: Andrew SullivanDate: 2003-10-05 14:34:31
Subject: Re: reindex/vacuum locking/performance?
Previous:From: Matt ClarkDate: 2003-10-05 11:14:24
Subject: Re: reindex/vacuum locking/performance?

pgsql-hackers by date

Next:From: Hans-Jürgen SchönigDate: 2003-10-05 13:41:03
Subject: Re: Thoughts on maintaining 7.3
Previous:From: Bruce MomjianDate: 2003-10-05 13:34:54
Subject: Re: Open 7.4 items

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group