| From: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
|---|---|
| To: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| 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: | 2016-10-03 11:25:17 |
| Message-ID: | 2c4038d9-9d41-1a58-765f-8139d6fe3fd5@iki.fi |
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| Lists: | pgsql-hackers |
On 10/03/2016 04:46 AM, Michael Paquier wrote:
> On Fri, Sep 30, 2016 at 8:10 PM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>> This patch set is in pretty good shape, the only problem is that it's so big
>> that no-one seems to have the time or courage to do the final touches and
>> commit it.
>
> Did you see my suggestions about simplifying its SQL structure? You
> could shave some code without impacting the base set of features.
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. Separate columns for the
functional dependencies, the MCVs, and the histogram, probably makes
sense anyway.
- Heikki
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