[postgis-users] ST_Union (8.4) and TopologyException

[Paul Ramsey]

It's odd for union to return no result.

The "high speed" union can only kick in when run against collections
consisting entirely of polygons. If you have a non-polygon, you'll get
the old behavior. You might even get the old behavior if you have a
null in there, that's a case I'm not sure of.

P.

On Fri, Aug 7, 2009 at 10:37 PM, Simon
Greener<simon at spatialdbadvisor.com> wrote:
> To those who asked for a test case.
>
> I prepared and sent a test case to Regina to ensure it was a good test set before sending it on to the discussion list.
>
> Regina tested it and reported to me that:
>
> "I tested this against GEOS 3.2 SVN and it worked.  Against GEOS 3.1.1 it doesn't."
>
> I was running GEOS 3.1.1 as part of the standard PostGIS 1.4 on PostgreSQL 8.4 combo.
>
> Regina provided me with the compiled GEOS 3.2 libraries:
>
> SELECT postgis_full_version();
> "POSTGIS="1.4.0" GEOS="3.2.0-CAPI-1.6.0" PROJ="Rel. 4.6.1, 21 August 2008" USE_STATS"
>
> I can confirm that my data is now successfully processed by PostGIS's ST_Union though it isn't all that fast:
>
> "Query returned successfully with no result in 5011922 ms." = 1hr 23min which is pretty slow.
>
> Any idea why?
>
> regards
> Simon
> --
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