Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> The existing opclasses only support distance-to-a-point, but I believe
> the KNN gist code is flexible enough that it could be used for distance
> to the edge of a shape as well. Someone just needs to write the
> operators and support functions.
The distance has to be exactly computable from the index entry, so you'd
need to store the whole shape in the index, not just a bounding box.
Not sure how practical that will be for complex shapes.
regards, tom lane