[postgis-devel] Is there a reason we don't have an ST_Intersection aggregate function

Nicklas Avén nicklas.aven at jordogskog.no
Mon Sep 1 01:37:55 PDT 2014

In general I think we could do a lot of cool things with aggregates.
I have had a thought in my head for a very long time that I haven't had time to investigate.

Quite often people is asking for a function like union in the esri world.

In PostGIS we have a problem to do calculations that involves more than 2 geoemtries.
But as an aggregate function it vould be possible to do.


2014-09-01 Paul Ramsey  wrote:

Only reason is nobody ever asked for it, it's hard to figure great use
>cases for it.
>On Sun, Aug 31, 2014 at 6:16 PM, Paragon Corporation wrote:
>> I wasn't sure if we just thought there wasn't much utility in it or if there
>> was a technical obstacle.
>> I would think that would be easier to build than the other aggregates since
>> as you add more geometries it shrinks and the current aggregate state is
>> always the result of the previous state plus new geometry (so no need for an
>> accumulation function or a final state function) and if you ever end up with
>> a  geometry collection, you short-circuit out.
>> Thanks,
>> Regina
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