Yes. Use ST_Dump to explode your MULTI* object, take the ST_Centroid of each,
and ST_Collect them together again.
SELECT ST_AsText(ST_Collect(the_geom))
FROM (
SELECT ST_Centroid((ST_Dump(the_geom)).geom) AS the_geom
FROM (
SELECT
'MULTIPOLYGON (
(( 0 0, 0 1, 1 1, 1 0, 0 0 )),
(( 2 2, 2 3, 3 3, 3 2, 2 2 ))
)'::geometry AS the_geom
) AS foo
) AS foo2;
st_astext
-----------------------------
MULTIPOINT(0.5 0.5,2.5 2.5)
(1 row)
Cheers,
Kevin
Mike Toews wrote:
Hi,
Is there a simple way to extract the multiple centroids as MULTIPOINT
geometries from MULTI* objects (i.e., ST_MULTICENTROID(geometry) )? The
ST_CENTROID function only returns POINT geometries.
(An example application of this is to initially place CAD labels for
MULTIPOLYGON features, since it appears that AutoCAD is not smart enough
to place these properly, and need manual adjustment to avoid label
conflicts. I have always been baffled by the purpose of multipoints
until now.)
I'm guessing this isn't a built-in function and the solution will be a
custom SQL or PL/pgSQL function. Thanks for any help/ideas.
-Mike
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