[geos-devel] Progress on #837 - TopologyException in UnaryUnion
dbaston at gmail.com
Tue Apr 16 08:21:09 PDT 2019
Either way, the union of a polygonal coverage is a common special case that
would benefit from having its own algorithm. I implemented this for PostGIS
a couple of years ago, though there didn't seem to be much interest at the
time . It's probably a better fit for GEOS anyway. I wrote a fairly ugly
Java implementation several years ago  that I could re-do to take
advantage of recent polygonizer improvements and bring into GEOS.
On Tue, Apr 16, 2019 at 11:06 AM Martin Davis <mtnclimb at gmail.com> wrote:
> That's good to know, Darafei. Can you provide a data example that we can
> use for doing performance testing?
> I'm not seeing that JTS buffer(0) is slower than union() on a random
> triangulation. So perhaps either your dataset has some different
> characteristic, or possibly GEOS buffer has different performance
> characteristics to JTS.
> On Tue, Apr 16, 2019 at 5:27 AM Darafei "Komяpa" Praliaskouski <
> me at komzpa.net> wrote:
>>> Ultimately I think the ideal approach is going to be abandoning
>>> CascadedUnion and switch to a full union algorithm (which will essentially
>>> be the same as running buffer(0). This should have very good performance.
>> We're using PostGIS's ST_Union to dissolve a clipped TIN into a polygon.
>> Current ST_Union implementation handles this measurably faster than
>> ST_Buffer(ST_Collect(geom),0). Please keep this case in mind.
>> Darafei Praliaskouski
>> Support me: http://patreon.com/komzpa
>> geos-devel mailing list
>> geos-devel at lists.osgeo.org
> geos-devel mailing list
> geos-devel at lists.osgeo.org
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