| From: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Mark Dilger <hornschnorter(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: improving GROUP BY estimation |
| Date: | 2016-04-02 12:20:13 |
| Message-ID: | CAEZATCVkTeN6fLvhcp=0EeKK091NCyOcO1mh9Znnk5GQp=N1+w@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 31 March 2016 at 22:02, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'm just concerned about what happens when the Dellera paper stops being
> available. I don't mind including that URL as a backup to the written-out
> argument I just suggested.
>
Here's an updated patch with references to both papers, and a more
detailed justification for the formula, along with the other changes
discussed. Note that although equation (2) in the Dell'Era paper looks
different from the Yao formula, it's actually the same.
Regards,
Dean
| Attachment | Content-Type | Size |
|---|---|---|
| estimate-num-groups-v5.patch | text/x-diff | 4.2 KB |
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