Re: multivariate statistics v14

From: Tatsuo Ishii <ishii(at)postgresql(dot)org>
To: tomas(dot)vondra(at)2ndquadrant(dot)com
Cc: ishii(at)postgresql(dot)org, robertmhaas(at)gmail(dot)com, david(at)pgmasters(dot)net, tgl(at)sss(dot)pgh(dot)pa(dot)us, alvherre(at)2ndquadrant(dot)com, petr(at)2ndquadrant(dot)com, jeff(dot)janes(at)gmail(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: multivariate statistics v14
Date: 2016-04-09 17:37:57
Message-ID: 20160410.023757.532440443943028713.t-ishii@sraoss.co.jp
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> But I still think it wouldn't move the patch any closer to committable
> state, because what it really needs is review whether the catalog
> definition makes sense, whether it should be more like pg_statistic,
> and so on. Only then it makes sense to describe the catalog structure
> in the SGML docs, I think. That's why I added some basic SGML docs for
> CREATE/DROP/ALTER STATISTICS, which I expect to be rather stable, and
> not the catalog and other low-level stuff (which is commented heavily
> in the code anyway).

Without "user-level docs" (now I understand that the term means all
SGML docs for you), it is very hard to find a visible
characteristics/behavior of the patch. CREATE/DROP/ALTER STATISTICS
just defines a user interface, and does not help how it affects to the
planning. The READMEs do not help either.

In this case reviewing your code is something like reviewing a program
which has no specification.

That's the reason why I said before below, but it was never seriously
considered.

>> - There are some explanation how to deal with multivariate statistics
>> in "14.1 Using Explain" and "14.2 Statistics used by the Planner"
>> section.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

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