Re: WITHIN GROUP patch

Atri Sharma <atri(dot)jiit(at)gmail(dot)com> writes:
> Please find attached the latest patch for WITHIN GROUP. This patch is
> after fixing the merge conflicts.

I've committed this after significant editorialization --- most notably,
I pushed control of the sort step into the aggregate support functions.
I didn't like the way nodeAgg.c had been hacked up to do it the other way.
There's a couple hundred lines of code handling that in orderedsetaggs.c,
which is more or less comparable to the amount of code that didn't get
added to nodeAgg.c, so I think the argument that the original approach
avoided code bloat is bogus.

The main reason I pushed all the new aggregates into a single file
(orderedsetaggs.c) was so they could share a private typedef for the
transition state value. It's possible that we should expose that
struct so that third-party aggregate functions could leverage the
existing transition-function infrastructure instead of having to
copy-and-paste it. I wasn't sure where to put it though --- maybe
a new include file would be needed. Anyway I left the point for
future discussion.

regards, tom lane