[postgis-devel] point_in_multipolygon implementation

[Mark Leslie]

Mose Andre wrote:
> In trunk, lwgeom_functions_analytic.c:1397 and thereabouts is a
> commented out point_in_multipolygon function.
>
> We have noticed a performance gain by convincing contains
> (lwgeom_geos_c:1388) to use the point_in_polygon shortcut, but our
> application uses a lot of multipolygons.  Rather than switch the
> client code to decompose multipolygons (most of them are a single
> polygon anyway) it would be nice to just implement this other
> shortcut.
>
> Does anyone know why it's not functional?  Or have any recommendations
> on how to fix it up?  I cannot find any discussion on the lists.
>
> Thanks,
> Mose
>
> >From lwgeom_functions_analytic.c:
>
> /*
>  * return 0 iff point is outside every polygon
>  */
>
> /* Not yet functional.
>
> int point_in_multipolygon(LWMPOLY *mpolygon, LWPOINT *point)
> {
>         int i;
>
> #ifdef PGIS_DEBUG_CALLS
>         lwnotice("point_in_multipolygon called.");
> #endif
>         for(i=1; i<mpolygon->ngeoms; i++)
>         {
>                 if(point_in_polygon((LWPOLY *)mpolygon->geoms[i],
> point)!=0) return 1;
>         }
>         return 0;
> }
> */
>
>
> >From lwgeom_geos_c.c:
>
>         /* Not yet functional
>         else if(type1 == MULTIPOLYGONTYPE && type2 == POINTTYPE)
>         {
>                 POSTGIS_DEBUG(3, "Point in MultiPolygon test
> requested...short-circuiting.");
>
>                 mpoly = lwmpoly_deserialize(SERIALIZED_FORM(geom1));
>                 point = lwpoint_deserialize(SERIALIZED_FORM(geom2));
>                 if(point_in_multipolygon(mpoly, point) == 0)
>                 {
>                         PG_FREE_IF_COPY(geom1, 0);
>                         PG_FREE_IF_COPY(geom2, 1);
>                         lwgeom_release((LWGEOM *)mpoly);
>                         lwgeom_release((LWGEOM *)point);
>                         PG_RETURN_BOOL(FALSE);
>                 }
>                 else
>                 {
>                         PG_FREE_IF_COPY(geom1, 0);
>                         PG_FREE_IF_COPY(geom2, 1);
>                         lwgeom_release((LWGEOM *)mpoly);
>                         lwgeom_release((LWGEOM *)point);
>                         PG_RETURN_BOOL(TRUE);
>                 }
>         }
>         */
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>   
The short story is that I wrote that when I did the point_in_polygon
implementation, figuring it was a trivial extension, but had enough bugs
in point_in_polygon that I ran out of time to test the
point_in_multipolygon.  There's no fundamental reason that I recall that
it doesn't work, I just couldn't say that it did, so it's left out.  If
you have time to run some tests with it uncommented and let me know the
results/report any bugs, we can get it working.

-- 
Mark Leslie
Geospatial Software Architect
LISAsoft

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