Re: polygon overlay

Gary Fu <gfu(at)sigmaspace(dot)com> writes:
> I don't see any overlap between the polygon and the box in the following
> sql. Can anyone explain why it returns 't'?

> select polygon(path '((0,0),(10,10),(20,10),(10,0))') && polygon(box
> '((16,0),(17,1))');
> ?column?
> ----------
> t
> (1 row)

Up to 8.4 the poly_overlap function did this:

* Determine if polygon A overlaps polygon B by determining if
* their bounding boxes overlap.
*
* XXX ought to do a more correct check!

I see it's been improved for 9.0 ...

regards, tom lane