From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com> |
Cc: | Bruce Momjian <bruce(at)momjian(dot)us>, 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: | 2011-01-20 14:19:00 |
Message-ID: | AANLkTi=OYC2dN1SkaSY5AEyOVd4Zu-YPTgW-YKV=+xsj@mail.gmail.com |
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Lists: | pgsql-performance |
On Thu, Jan 20, 2011 at 4:17 AM, Cédric 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"?
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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