| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | "Jim C(dot) Nasby" <decibel(at)decibel(dot)org> |
| Cc: | Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>, pgsql(at)mohawksoft(dot)com, Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>, Mark Kirkwood <markir(at)coretech(dot)co(dot)nz>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Query optimizer 8.0.1 (and 8.0) |
| Date: | 2005-02-20 19:36:43 |
| Message-ID: | 200502201936.j1KJahU15443@candle.pha.pa.us |
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| Lists: | pgsql-hackers |
Jim C. Nasby wrote:
> On Mon, Feb 14, 2005 at 09:55:38AM -0800, Ron Mayer wrote:
>
> > I still suspect that the correct way to do it would not be
> > to use the single "correlation", but 2 stats - one for estimating
> > how sequential/random accesses would be; and one for estimating
> > the number of pages that would be hit. I think the existing
> > correlation does well for the first estimate; but for many data
> > sets, poorly for the second type.
>
> Should this be made a TODO? Is there some way we can estimate how much
> this would help without actually building it?
I guess I am confused how we would actually do that or if it is
possible.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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