Mike , I just tested this layer with a draft version of our new unioning approach. - it completes in 10 seconds. Not great but better than the current ST_Union approach.
In OpenJump by the way which is using a not quite as sophisticated algorithm as Martin's cascaded union, the below completes in 3 seconds. So not to worry - next version (1.3.4) I'm sure we'll be much closer to ArcMap in speed, and in version 1.4 - we might even beat ArcMap. Martin, This is a much more simplified version of the dataset I gave you yesterday to test with where your approach completed in 20 seconds (with 2895 records). This one doesn't choke openjump as the one I gave you does and only has 273 records Hope that helps, Regina ---------------------------------------------------------------------------- ---------------------------------------------------------------------------- ----------------------------------------------------------- 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 _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users