Re: group by points

Bruno Wolff III <bruno(at)wolff(dot)to> writes:
> On Mon, May 22, 2006 at 10:23:28 +0200,
> Albe Laurenz <all(at)adv(dot)magwien(dot)gv(dot)at> wrote:
>> In order to (efficiently) process a GROUP BY clause, you need a
>> total ordering on the data type that you group by, i.e. an ordering
>> such that for any two data x and y you have either x < y or x > x
>> or x = y.

> An equality operator is good enough if the number of unique groups isn't too
> large, so that a hash aggregate plan works efficiently.

Doesn't help for the case at hand, since point_eq isn't marked hashable
either. It would be good to fix things so that the system doesn't
insist on having the sorting option available, though.

regards, tom lane