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: | pgsql-committers(at)postgresql(dot)org |
Subject: | Re: pgsql-server/src/backend/utils/sort tuplesort.c |
Date: | 2004-03-18 03:06:18 |
Message-ID: | 200403180306.i2I36Ig01265@candle.pha.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-committers |
Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Tom Lane wrote:
> >> During btree index build, sort equal-keyed tuples according to their
> >> TID (heap position). This doesn't do anything to the validity of the
> >> finished index, but by pretending to qsort() that there are no really
> >> equal keys in the sort, we can avoid performance problems with qsort
> >> implementations that have trouble with large numbers of equal keys.
> >> Patch from Manfred Koizar.
>
> > I think there is also the advantage that many equal keys will access the
> > heap in a more sequential, rather than random, order, which is the part
> > that really excited me.
>
> But we aren't attempting to maintain that ordering after index build.
> (In fact, it was exactly that point that triggered the argument last
> time round ...)
Agreed, but we don't maintain CLUSTER either. I see no harm in having
it start out ordered, at least.
--
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
From | Date | Subject | |
---|---|---|---|
Next Message | Bruce Momjian | 2004-03-18 03:56:59 | pgsql-server/src/tools/fsync Makefile README t ... |
Previous Message | Tom Lane | 2004-03-18 00:37:01 | Re: pgsql-server/src/backend/utils/sort tuplesort.c |