Skip site navigation (1) Skip section navigation (2)

Re: Group-count estimation statistics

From: Kris Jurka <books(at)ejurka(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Greg Stark <gsstark(at)mit(dot)edu>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Group-count estimation statistics
Date: 2005-01-28 21:30:00
Message-ID: Pine.BSO.4.56.0501281628001.23832@leary.csoft.net (view raw or flat)
Thread:
Lists: pgsql-hackers

On Fri, 28 Jan 2005, Tom Lane wrote:

> you don't GROUP BY unique combinations of columns over huge
> tables --- or at least, you shouldn't expect great performance if you do.

The proposed change biases towards a hash plan which has no provision for
spilling to disk.  Slow is one thing, but excessive memory usage and
possibly failing is another thing.

Kris Jurka

In response to

Responses

pgsql-hackers by date

Next:From: Merlin MoncureDate: 2005-01-28 21:36:05
Subject: Re: Allow GRANT/REVOKE permissions to be applied to all schema objects with one command
Previous:From: Bruno Wolff IIIDate: 2005-01-28 21:03:19
Subject: Re: Allow GRANT/REVOKE permissions to be applied to all schema objects with one command

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group