Subject: Re: group by not returning sorted rows
From: Bret Hughes <bhughes@elevating.com>
To: postgresql sql list <pgsql-sql@postgresql.org>
In-Reply-To: <16211.1081204461@sss.pgh.pa.us>
References: <1081202143.18380.117.camel@bretsony>
	<16211.1081204461@sss.pgh.pa.us>
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Date: 06 Apr 2004 11:51:36 -0500
Message-Id: <1081270297.18380.142.camel@bretsony>
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On Mon, 2004-04-05 at 17:34, Tom Lane wrote:
> Bret Hughes <bhughes@elevating.com> writes:
> > and the rows resulting from the query are no longer sorted by log date. 
> > Is this a change since 7.2x?
> 
> Yes.  7.4 can use hashing instead of sorting to bring grouped rows
> together.
> 
> > I can achieve the results I need by adding an order by clause identical
> > to the group by but this seems counter intuitive since the rows have to
> > be ordered anyway.
> 
> No they don't; you're making an assumption about the implementation that
> is no longer warranted.  The SQL spec doesn't require it either ...
> output ordering is only guaranteed if you specify ORDER BY, per spec.
> 
> 			regards, tom lane

Thanks, 

I replied to Tom directly by accident and did not want the list to think
I was ungrateful for the quick reply :)

Bret