[geos-devel] Should DistanceWithin(EMPTY, ANYTHING, ANYDISTANCE) always return false ?

[Darafei "Komяpa" Praliaskouski]

Points on infinite distance are still on the extended R2+ plane. The empty
points aren't.

This one should be "always false", and make sure that "POINT(INF INF)" is
at INF distance from anything (can be true). POINT(Inf Inf) != POINT(NaN
NaN) in this aspect.

On Mon, Oct 4, 2021 at 6:50 PM Paul Ramsey <pramsey at cleverelephant.ca>
wrote:

> https://trac.osgeo.org/postgis/wiki/DevWikiEmptyGeometry
>
>
> pramsey=# select st_distance('POINT(1 1)','POINT EMPTY');
>  st_distance
> -------------
>
> (1 row)
>
> Interesting note in the wiki about returning NULL for DWithin.
>
> Current behaviour.
>
> pramsey=# select st_dwithin('POINT(1 1)','POINT EMPTY', 1);
>  st_dwithin
> ------------
>  f
> (1 row)
>
> pramsey=# select st_dwithin('POINT(1 1)','POINT EMPTY', 'Inf'::float8);
>  st_dwithin
> ------------
>  t
> (1 row)
>
> I could see going for "always false" since we're almost there for non-inf
> values.
>
> P
>
> > On Oct 4, 2021, at 8:08 AM, Sandro Santilli <strk at kbt.io> wrote:
> >
> > On Mon, Oct 04, 2021 at 05:02:24PM +0200, Sandro Santilli wrote:
> >> I'd think yes, honestly, but the current code returns TRUE sometimes,
> >> particularly for MAXDISTANCE being Infinite...
> >>
> >> As I think GEOS is not being used by phylosophers, I can't find any
> >> reason why would anyone want a TRUE result from a DistanceWithin()
> >> query involving an EMPTY geometry.
> >
> > We have the same issue on PostGIS:
> > https://trac.osgeo.org/postgis/ticket/5008
> >
> > --strk;
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