[postgis-users] PostGIS 1.3.3 on Windows XP Unstable

Wed Aug 13 09:52:29 PDT 2008

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> Would probably be more efficiently done with
> 
> SELECT  gid, ST_Collect(ScrubPolygon(geom)) As scrubbedgeom
> FROM
> 	(SELECT gid, (ST_Dump(the_geom)).geom
> 			FROM tabletoscrub) As foo
> GROUP By gid ;
> 
> The reason being is that ST_GeometryN is quite inefficient when
dealing
> with
> large numbers of geometries.  So if you plan to dump out all
geometries
> use
> ST_Dump instead.

Thank you, Regina. That cleaned up the weird nested collections that
were being created and also simplified the function to just this:

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

> Also would be nice if you posted this to the wiki when you are done.

Sure thing.

I'm almost there. The function works beautifully except on a few
geometries. These geometries produce messages like the following when I
call ST_IsValid:

NOTICE:  Nested shells at or near point -76.554 38.8815

I'm not sure what "nested shell" means. At first thought it says to me
that one external polygon is contained inside another external polygon,
but isn't that legal?