From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
cc: Dean Rasheed <dean.a.rasheed@gmail.com>,
        Tomas Vondra <tomas.vondra@2ndquadrant.com>,
        Alexander Korotkov <a.korotkov@postgrespro.ru>,
        Mark Dilger <hornschnorter@gmail.com>,
        PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: improving GROUP BY estimation
In-reply-to: <20160331205118.GA166096@alvherre.pgsql>
References: <20160331205118.GA166096@alvherre.pgsql>
Comments: In-reply-to Alvaro Herrera <alvherre@2ndquadrant.com>
	message dated "Thu, 31 Mar 2016 17:51:18 -0300"
Date: Thu, 31 Mar 2016 17:02:56 -0400
Message-ID: <8033.1459458176@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-hackers-owner@postgresql.org

Alvaro Herrera <alvherre@2ndquadrant.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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