Re: multi-column aggregates

Tom Lane wrote:

>Chris Kratz <chris.kratz@vistashare.com> writes:
>
>
>>Thanks for the reply.  Yes, subselects would work very well and in some ways
>>are more elegant then the hand waving we had to do to get the multi-column
>>aggregates to work.
>>
>>
>
>BTW, there is not any fundamental reason why we can't support aggregate
>functions with multiple inputs.  I looked at this not long ago and
>determined that the major stumbling blocks would be
>(1) trying to keep the code in nodeAgg.c from getting a lot more
>complicated and hence slower for the single-input case;
>(2) figuring out how to change the syntax for CREATE AGGREGATE.
>
>It certainly seems doable if someone wants to spend time on it.
>
>
I did some work a couple months ago (and posted here
"http://archives.postgresql.org/pgsql-general/2005-11/msg01214.php") on
developing composite aggregates for linear-regression, and while at first I was a bit dissatisfied with having to cast
mydata pairs as POINT data type, once I got confortable with that it made a lot of sense. 

Regards,
Berend Tober