[postgis-users] Polygonize questions

[strk at refractions.net]

On Sat, Nov 12, 2005 at 03:04:36PM -0700, Charlie Savage wrote:
> Couple of questions about polygonize.
> 
> * Why does it return a GeometryCollection instead of a MultiPolygon?

Because it's really a collection of polygons, not a MultiPolygon.
A MultiPolygon must meet certain constraints in order to be valid
(polygons must not intersect) and Polygonize doesn't try to enforce
this.

> * Is there a way to convert a GeometryCollection returned by polygonize 
> to a MultiPolygon?  Is there any advantage to doing this?

Check out the dump() and collect() functions.

--strk;

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