| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Multivariate statistics and expression indexes |
| Date: | 2017-02-21 00:49:34 |
| Message-ID: | 20170221004934.GB13919@momjian.us |
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| Lists: | pgsql-hackers |
On Tue, Feb 21, 2017 at 01:27:53AM +0100, Tomas Vondra wrote:
> On 02/21/2017 12:13 AM, Bruce Momjian wrote:
> >At the risk of asking a stupid question, we already have optimizer
> >statistics on expression indexes. In what sense are we using this for
> >multi-variate statistics, and in what sense can't we.
> >
>
> We're not using that at all, because those are really orthogonal features.
> Even with expression indexes, the statistics are per attribute, and the
> attributes are treated as independent.
>
> There was a proposal to also allow creating statistics on expressions
> (without having to create an index), but that's not supported yet.
OK, thanks. I had to ask.
--
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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