[postgis-users] converting multipolygon to polygon
Helge Jensen
hej at actua.dk
Mon Nov 16 00:07:41 PST 2009
I just wanna inject a comment about performance here.
Using GeometryN (or ST_GeometryN) incurs a significant penalty, especially
in terms of memory when i was using it. ST_Dump performs *much* better.
>From searches on the internet i concluded that the standard way that
geometries are passed between functions by-value. So invoking GeometryN N
times becomes rather expensive for large geometries.
ST_Dump returns an array of information from which you can easily extract
the parts:
SELECT dump.geom FROM ST_Dump(orig_geom) as dump;
--
Helge Jensen
Partner & Senior Software Developer
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