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Re: Problem with ORDER BY and DISTINCT ON

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Steve Midgley <public(at)misuse(dot)org>
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: Problem with ORDER BY and DISTINCT ON
Date: 2008-07-31 22:51:32
Message-ID: 24728.1217544692@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-sql
Steve Midgley <public(at)misuse(dot)org> writes:
> At 07:29 AM 7/16/2008, Tom Lane wrote:
>> I think what is happening is that ORDER BY knows that and gets rid of
>> the duplicate entries while DISTINCT ON fails to do so.

> Of course removing the duplicate from both areas is the correct 
> solution and I broke down and hacked that into the auto-sql-writing 
> code and so my immediate problem is solved. I'm happy to file this as a 
> ticket for Pg (please point me to your ticket tool as I've never used 
> it). This is not a very big deal but Pg has such a high compliance with 
> wacky-but-valid SQL it does seem like it should be fixed just because. 

I've applied a patch for this to CVS HEAD.  I doubt we'll try to fix it
in the back branches, though --- it's too much of a corner case to be
worth taking any risk of breaking other stuff.

			regards, tom lane

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Subject: Function returning setof taking parameters from another table

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