From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomasz Myrta <jasiek@klaster.net>
Cc: Richard Huxton <dev@archonet.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: order by and aggregate
Date: Mon, 06 Jan 2003 11:36:58 -0500
Message-ID: <14758.1041871018@sss.pgh.pa.us> (raw)
In-Reply-To: <3E198E18.5090408@klaster.net>
References: <3E197A39.8070808@klaster.net>
<200301061341.32945.dev@archonet.com>
<3E198E18.5090408@klaster.net>
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
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, jasiek@klaster.net, dev@archonet.com
Subject: Re: order by and aggregate
In-Reply-To: <14758.1041871018@sss.pgh.pa.us>
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