[postgis-users] PostGIS 1.3.3 on Windows XP Unstable

Wed Aug 13 10:35:35 PDT 2008

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> Martin Davis wrote:
> That's what it means, alright.  It is invalid to have one polygon
inside
> another one in the same MultiPolygon.  (If you post the invalid
geometry
> I can confirm that this is what is happening).
> 
> Bottom line is that you need to check for two things:
> - holes which have "flipped" to be outside their parent shell
> - polygons which have flipped to be inside another polygon

Ah ok. That is the problem. Is the fix as simple as calling ST_Union()
on the constituent polygons instead of ST_Collect?

create function ScrubMultiPolygon(input geometry) returns geometry as $$
begin
	return (select ST_Union(ScrubPolygon(geom)) from (select
(ST_Dump(input)).geom) as x);
end;
$$ LANGUAGE plpgsql;

This appears to work, but I'm not sure if it is the most efficient
solution.