Re: cost_nonsequential_access()

From: Manfred Koizar <mkoi-pg(at)aon(dot)at>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: cost_nonsequential_access()
Date: 2004-06-08 15:50:58
Message-ID: 9hmbc0pioq7283m6i5dmja3dbl495eceej@email.aon.at
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On Tue, 08 Jun 2004 11:13:43 -0400, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>This patch seems to do considerably more violence to the equations than
>is needed to cover that oversight, though. The old behavior was
>intentionally nonlinear in relsize; this is not.

The comment says "entirely ad-hoc" and I didn't see a particular reason
why the lower half should be nonlinear in relsize while the upper half
is linear in 1/relsize. So I opted for the "more esthetic" symmetrical
function. :-)

http://www.pivot.at/pg/costsize.jpg original
http://www.pivot.at/pg/costsize_2.jpg nonlinear/linear
http://www.pivot.at/pg/costsize_3a.jpg nonlinear
http://www.pivot.at/pg/costsize_3b.jpg linear

I don't have a strong opinion for either relsize or relsize^2. So
please add " * relsize" or " / relsize" as appropriate before you apply
(if you intend to apply).

Servus
Manfred

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