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

[G. Allegri]

I forgot to say, I'm working on Windows XP, Postgresql 8.4.4, Postgis 1.5.0

2010/6/22 G. Allegri <giohappy at gmail.com>:
> 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
>