Re: Aggregate ORDER BY patch

>>>>> "Heikki" == Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:

>> No artificial restrictions are imposed on what syntactical
>> combinations are allowed. However, ORDER BY is not allowed with
>> aggregates used as window functions (as per the existing
>> restriction on DISTINCT).

Heikki> How is this different from window functions?

Window functions return a row for each row of input, aggregates don't.

The reason I didn't tackle the case of aggregate functions used as
window functions is that the spec allows constructs like this:

array_agg(a order by b) over (order by c)

which can't be represented using the aggregate-as-window-function
mechanism as it currently stands, since you'd have to re-sort the
window each time.

--
Andrew (irc:RhodiumToad)