-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 > It's your bad luck to have geometries that make PostGIS fail... 8^) > > If there's geometries which cause problems with certain operations, the > most helpful thing to do is to post them along with a description of the > problem. That gives a fighting chance to fix them when further > development is done.
The problem of ST_SimplifyPreserveTopology() producing geometries that ST_Union() chokes on is already known. When I tried to scrub the polygons I ran into performance problems, particularly with ST_Union(geometry). I ran into similar performance problems with Oracle's sdo_aggro_union(). > So Java2D worked on your problem? I have to admit, I'm impressed how > robust Java2D is. If I could understand their algorithm I'd be keen on > trying to follow their approach to get the same level of robustness in > JTS/GEOS... Yes, Java2D was able to perform a union on the geometries produced by ST_SimplifyPreserveTopology() and it does the union relatively fast. The only thing I have found that beats Java2D is ArcGIS. In one test I did I performed a union of the USGS state boundaries (http://www.census.gov/geo/cob/bdy/st/st00shp/st99_d00_shp.zip). Here are the results: Oracle 11.1: 25 min PostGIS 1.3.3: 42 sec Java2D 1.5: 4 sec ArcMap 9.2: 1 sec Any thoughts why PostGIS is about 40x slower than ArcMap at this operation? Any thoughts why Oracle takes 25 min? lol The bottleneck in my application now looks to be ST_SimplifyPreserveTopology(). I'm finding that it's often best to do computation outside the database. However, one thing that Java2D is missing is a polygon simplification function. I might look to see if Geotools has one. -----BEGIN PGP SIGNATURE----- Version: PGP Universal 2.8.3 Charset: us-ascii wsBVAwUBSKS4Vh6WPRoYuvd0AQjehAf+LetIb4Q+xMXZZiPkJmT8rteWMPeDYPor i31cLgjIvY1x7WZZ8V95rSnjYfpARlqbInxwjM4tXAz17kfOUJfnbMS13N/DDCDT IxpHDuim3/HGDMweqP//GNMfpHwK5a8hPZeHlZrTvL62EOZ4F7gyzIJ3ZBkHMikS KshFkiHfIyoThVXRHX9mdzEmQAR57zGKEid3S3Q97ESelbk8/GqSZB0PY6LYJ0xj MLoHeAYDrKwNCSI2bHxXhtP4fSwGaN7KkZ6unzG/QOb6YOzxmSAx4/KE89KBCmnC 2yXCX8v3ONi8Vucti7lZ29DHDbE9Q6HP7wLeWnOtXKm/n8DoIlfhOw== =BHDB -----END PGP SIGNATURE----- _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
