[postgis-users] Topological Exceptions

Obe, Regina robe.dnd at cityofboston.gov
Tue Mar 11 04:49:45 PDT 2008

I've been doing a lot of work using ST_Intersection, ST_Difference,
ST_Union etc to cut out slices of geometries I don't want and slicing up
geometries into smaller pieces, reunioning etc.
I've been running into a lot of Topological Exceptions of the form
directed Edge this and non-noded that.  For the most part I've been able
to overcome these by slicing things smaller or skipping over problem
regions (e.g. areas where the difference is a line or point or something
of that sort).
I think a lot of people have run into the same issues and have gotten
frustrated and there doesn't seem to be a simple solution suggested to
overcome these.
Is there any way we can change (add overloaded functions or some setting
parameter) - that take additional parameters to simply ignore these
errors that says return empty collection or NULL when a GEOS error is
thrown.  That way I can simply ignore these and throw them out of my
equation and move on.
Just a thought.  I'm sure my suggestion is rather simple-minded and I'm
sure I'm missing some reason of why this is not feasible.  An
explanation of why my suggestion is stupid at anyrate would be nice.

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