| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Do we need multi-column frequency/histogram stats? WAS Re: Statistics "dependency" |
| Date: | 2017-04-23 14:16:57 |
| Message-ID: | 20170423141657.GA16241@momjian.us |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
On Sun, Apr 23, 2017 at 10:01:16AM -0400, Bruce Momjian wrote:
> On Sun, Apr 23, 2017 at 11:44:12AM +0100, Simon Riggs wrote:
> > For us "functional dependency" would sound like something to do with
> > functions (e.g. CREATE FUNCTION), so just "dependency" appears to me
> > to be the best term for this.
> >
> > There are multiple statistics for dependency stored, hence
> > "dependencies". I don't like it, but its the best term I can see at
> > present.
>
> OK, thank you for the reply, and I am sorry I forgot the previous
> discussion. I just wanted to re-check we had research this. Thanks.
(Email subject updated.)
Actually, I have a larger question that I was thinking about. Because
we already have lots of per-column stats, and now the dependency score,
is it possible to mix the per-column stats and dependency score in a way
that multi-column frequency/histogram stats are not necessary? That
might be a less costly approach I had not considered.
Or did I miss that discussion too? ;-)
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ As you are, so once was I. As I am, so you will be. +
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