ST_IsEmpty doesn't seem to work for me and I don't see the MultiPolygon
being converted to a GeometryCollection.
civics=# SELECT astext(wkb_geometry) FROM scale150000 LIMIT 1;
astext
------------------------
MULTIPOLYGON(( EMPTY))
(1 row)
civics=# SELECT ST_IsEmpty(wkb_geometry) FROM scale150000 LIMIT 1;
st_isempty
------------
f
(1 row)
ST_NPOINTS works. It seems like there should be a more direct way.
Sean
On 2008-07-04 12:03:33 -0400, Martin Davis <[EMAIL PROTECTED]> said:
Actually JTS/GEOS handle empty MultiPolygons just fine. I don't know why
the MULTIPOLYGON EMPTY is being converted to a general
GeometryCollection - I think this must be something that is being done
by PostGIS.
Seems like the answer is to use ST_IsEmpty. Doing text comparisons is
always going to be risky.
Kevin Neufeld wrote:
I believe that an empty multipolygon is converted into an empty
geometrycollection in JTS and hence PostGIS.
postgis=# SELECT ST_AsText('MULTIPOLYGON EMPTY'::geometry);
st_astext
--------------------------
GEOMETRYCOLLECTION EMPTY
(1 row)
postgis=# SELECT ST_IsEmpty('MULTIPOLYGON EMPTY'::geometry);
st_isempty
------------
t
(1 row)
Alternatively, I suppose you could get the number of points in the geometry.
postgis=# SELECT ST_NPoints('MULTIPOLYGON EMPTY'::geometry);
st_npoints
------------
0
(1 row)
Cheers,
Kevin
Sean Fulton wrote:
How do I test for an empty feature such as 'MULTIPOLYGON(( EMPTY ))' ?
IsEmpty seems to work only for collections.
astext(wkb_geometry) = 'MULTIPOLYGON(( EMPTY ))' doesn't seem to work.
Thanks,
Sean
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