Re: anti-join chosen even when slower than old plan

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Mladen Gogala <mladen(dot)gogala(at)vmsinfo(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: anti-join chosen even when slower than old plan
Date: 2011-01-27 01:40:50
Message-ID: 201101270140.p0R1eoH20105@momjian.us
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Robert Haas wrote:
> On Thu, Jan 20, 2011 at 4:17 AM, C?dric Villemain
> <cedric(dot)villemain(dot)debian(at)gmail(dot)com> wrote:
> >>> I think his point is that we already have a proven formula
> >>> (Mackert-Lohmann) and shouldn't be inventing a new one out of thin air.
> >>> The problem is to figure out what numbers to apply the M-L formula to.
> >>>
> >>> I've been thinking that we ought to try to use it in the context of the
> >>> query as a whole rather than for individual table scans; the current
> >>> usage already has some of that flavor but we haven't taken it to the
> >>> logical conclusion.
> >>
> >> Is there a TODO here?
> >
> > it looks like, yes.
>
> "Modify the planner to better estimate caching effects"?

Added to TODO.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +

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