Re: Aggregate ORDER BY patch

From: Greg Stark <gsstark(at)mit(dot)edu>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Aggregate ORDER BY patch
Date: 2009-11-13 09:42:35
Message-ID: 407d949e0911130142l12c98732w3aa7d1d4a63d3642@mail.gmail.com
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On Fri, Nov 13, 2009 at 7:54 AM, Heikki Linnakangas
<heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:
> Andrew Gierth wrote:
>> Herewith a patch to implement agg(foo ORDER BY bar) with or without
>> DISTINCT, etc.
>
> What does that mean? Aggregate functions are supposed to be commutative,
> right?

We certainly have non-commutative agggregates currently, notably array_agg()

I suspect it would be good to have a flag marking the commutative ones

--
greg

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