Subject: Re: multivariate statistics v8
To: Alvaro Herrera <alvherre@2ndquadrant.com>,
 Bruce Momjian <bruce@momjian.us>
References: <20160120215416.GA378214@alvherre.pgsql>
Cc: Robert Haas <robertmhaas@gmail.com>,
 "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <56A00ABD.9020207@2ndquadrant.com>
Date: Wed, 20 Jan 2016 23:31:25 +0100
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On 01/20/2016 10:54 PM, Alvaro Herrera wrote:
> Bruce Momjian wrote:
>> On Wed, Jan 20, 2016 at 02:20:38PM -0500, Robert Haas wrote:
>>> On Wed, Dec 23, 2015 at 2:07 PM, Tomas Vondra
>>> <tomas.vondra@2ndquadrant.com> wrote:
>>>>     The remaining question is how unique the statistics name should be.
>>>>     My initial plan was to make it unique within a table, but that of
>>>>     course does not work well with the DROP STATISTICS (it'd have to
>>>>     specify the table name also), and it'd also now work with statistics
>>>>     on multiple tables (which is one of the reasons for abandoning ALTER
>>>>     TABLE stuff).
>>>>
>>>>     So I think it should be unique across tables. Statistics are hardly
>>>>     a global object, so it should be unique within a schema. I thought
>>>>     that simply using the schema of the table would work, but that of
>>>>     course breaks with multiple tables in different schemas. So the only
>>>>     solution seems to be explicit schema for statistics.
>>>
>>> That solution seems good to me.
>>>
>>> (with apologies for not having looked at the rest of this much at all)
>>
>> Woh, this will be an optimizer game-changer, from the user perspective!
>
> That is the intent. The patch is huge, though -- any reviewing help
> is welcome.

It's also true that a significant fraction of the size is documentation 
(in the form of comments). However even after stripping them the patch 
is not exactly small ...

I'm afraid it may be rather difficult to understand the general idea of 
the patch. So if anyone is interested in discussing the patch in 
Brussels next week, I'm available.

Also, in December I've posted a link to a "paper" I started writing 
about the stats:

     https://bitbucket.org/tvondra/mvstats-paper/src


regards

--
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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