Hi,

I try

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

It seem work pretty fast and result seem ok.

Andrea.


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):
http://www.giovanniallegri.it/share/postgis_selection.zip

thanks a lot,

Giovanni


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