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To: Tomasz Myrta <jasiek@klaster.net>
Cc: Richard Huxton <dev@archonet.com>, pgsql-sql@postgresql.org
Subject: Re: order by and aggregate 
In-reply-to: <3E198E18.5090408@klaster.net> 
References: <3E197A39.8070808@klaster.net>
	<200301061341.32945.dev@archonet.com>
	<3E198E18.5090408@klaster.net>
Comments: In-reply-to Tomasz Myrta <jasiek@klaster.net>
	message dated "Mon, 06 Jan 2003 15:09:28 +0100"
Date: Mon, 06 Jan 2003 11:36:58 -0500
Message-ID: <14758.1041871018@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Tomasz Myrta <jasiek@klaster.net> writes:
> Standard Postgresql aggregate functions don't need sorted data, but my 
> function needs. Look at the data:
> <value>   <sum>
> 3	  3
> -2        1
> 6         7 *** max_sum=7
> -3        4
> 2         6

But if the input data is sorted into increasing order, then the largest
running sum value is always at the end.  Therefore max(sum()) is
equivalent to sum(); therefore you do not need the special aggregate,
nor the ordering.

			regards, tom lane