[postgis] How to indentify each polygons' donut polygons in multipolygon
dblasby at refractions.net
Tue Dec 18 09:16:47 PST 2001
> Hisaji ONO wrote:
> I've currently developed GML 2.0 convesion code from PostGIS's WKT.
> I've known PostGIS's NumInteriorRings & InteriorRingN function can
> deal with interior rings in polygons. But InteriorRingN function
> seemed to support "single" polygons.
> How to identify whether each polygons within
> multipolygon have interior rings or not?
This is, unfortunately, a problem with the OGC spec - its difficult to
directly access anything in a collection (ie. MULTI* or
Use the GeometryN(geometry,integer) function to get a sub-geometry. Ie.
To find out how many interior rings are in polygon #2.
(the_geom) must be a multi* or geometrycollection.
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