[postgis-users] st_union returning null on various (valid) sets of polygons/multipolygons

Andrea Peri 2007 aperi2007 at gmail.com
Tue Jun 22 13:57:46 PDT 2010


I try

    1 as id,
    st_union(a.geom) as geom
    public._postgis_selezione_ok as a

It seem work pretty fast and result seem ok.


>I'm trying to apply ST_Union on a set of geometries (multypolygons,
>most of which containing a single geometry), to test the CascadedUnion
>performance, but the most of times it returns a null result. I haven't
>been able to find a rule: sometimes it seems to be the number of
>geometries, sometimes the order, etc.
>Could someone replicate it? Here is a small selection of my layer (it
>contains already validated geometries):
>thanks a lot,

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