[postgis-users] ST_Union (8.4) and TopologyException

[Maxime van Noppen]

On 08/05/09 12:46, Paragon Corporation wrote:
> Mark,
> 
> To add I think Simon's dataset was too big to go thru 1.3 at a decent time
> (as I recall think its about 3000 polygons he's dealing with).  I think I
> have run into some of these issues myself in my torture tests but ignored
> them since they passed regress (I mean all versions failed) and I didn't
> absolutely verify they weren't invalid, but I'll try to dig some of these up
> to verify they were invalid.  
> 
> I suspect its a 1.3 issue as well, but I expect we'll see more of these
> kinds of things popping up as people will be more able to handle larger
> geometries and thus will be stress testing PostGIS more.

I run into this kind of problem every now and then. I've created a
ticket (http://trac.osgeo.org/geos/ticket/275) with a test case. The
problem still exists with geos-3.1.1. That specific test case works when
unioned in PostGIS rather than geos though.

When I encounter this kind of problem I usually simplify and/or snap to
grid my geometries and with a bit of luck it works again :).

-- 
Maxime