Re: multivariate statistics (v19)

From: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
To: Heikki Linnakangas <hlinnaka(at)iki(dot)fi>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tatsuo Ishii <ishii(at)postgresql(dot)org>, David Steele <david(at)pgmasters(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Álvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Petr Jelinek <petr(at)2ndquadrant(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: multivariate statistics (v19)
Date: 2016-10-04 03:25:08
Message-ID: CAB7nPqStJ9rb7zTPrnNHDhM4qOkxM9ETzg4d=8zT6yiT_rv7vw@mail.gmail.com
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On Mon, Oct 3, 2016 at 8:25 PM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> Yeah. The idea was to use something like pg_node_tree to store all the
> different kinds of statistics, the histogram, the MCV, and the functional
> dependencies, in one datum. Or JSON, maybe. It sounds better than an opaque
> bytea blob, although I'd prefer something more relational. For the
> functional dependencies, I think we could get away with a simple float
> array, so let's do that in the first cut, and revisit this for the MCV and
> histogram later.

OK. A second thing was related to the use of schemas in the new system
catalogs. As mentioned in [1], those could be removed.
[1]: https://www.postgresql.org/message-id/CAB7nPqTU40Q5_NSgHVoMJfbyH1HDtqMbFDJ+kwFJSpam35b3Qg@mail.gmail.com.

> Separate columns for the functional dependencies, the MCVs,
> and the histogram, probably makes sense anyway.

Probably..
--
Michael

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