Re: Aggregate ORDER BY patch

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
Cc: peter_e@gmx.net (Peter Eisentraut), Greg Stark <gsstark@mit.edu>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, pgsql-hackers@postgresql.org
Date: 2009-11-13T17:09:16Z
Lists: pgsql-hackers
Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> "Peter" == Peter Eisentraut <peter_e@gmx.net> writes:
>  Peter> This is exactly the syntax that is in the spec AFAICT.

> Right. The spec defines this syntax for array_agg and xmlagg (only).

Cool, I had forgotten that they added that in the latest revisions.
I withdraw the complaint that this patch goes too far beyond the spec.

> But it would be entirely unreasonable, the way postgres works, to
> implement ORDER BY for only specific aggregates.

Quite.  This is another instance of the thing I complained of before,
that the SQL committee likes to define the behavior of specific
aggregates instead of inducing a generic aggregate-behavior definition.
So we're on our own to extract one, and this proposal seems pretty
reasonable to me: it's useful and it's consistent with the query-level
behavior of DISTINCT and ORDER BY.

			regards, tom lane