| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(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: | 2016-03-31 21:02:56 |
| Message-ID: | 8033.1459458176@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> Tom Lane wrote:
>> See "Approximating block accesses in database organizations", S. B. Yao,
>> Communications of the ACM, Volume 20 Issue 4, April 1977 Pages 260-261
> That sounds nice all right, but I'm not sure it's actually helpful,
> because the article text is not available anywhere. I doubt most people
> will spend 15 bucks to buy that paper ... so we don't actually know
> whether the paper supports the chosen formula :-) unless you have a
> CACM subscription and can verify it.
Well, I do and I did, see my previous response.
> I think it's good to have the ACM reference anyway, for posterity, but
> it'd be good to (additionally) have something that people can read.
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.
regards, tom lane
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