On Tue, Nov 18, 2014 at 08:26:29PM +0100, Rémi Cura wrote: > This is suprising indeed. > Im my test using the v.out.postgis was still way faster than constructing > with postgis topology (about x3 I think). > > Are you using v.out.postgis -l, with grass 7?
Yes. The topology was pretty big, maybe that's the difference. Here's the dataset (not sure if still accessible): http://lists.osgeo.org/pipermail/postgis-devel/2014-January/024085.html GRASS 7.0.0beta3 (world):~ > v.info -t map=million_poly_topo1 nodes=3247661 points=0 lines=0 boundaries=5102420 centroids=1161248 areas=1855936 islands=1177 primitives=6263668 map3d=0 > Now I think I should have used a python way from within grass (grass offers > full binding, so it should be doable to loop trough grass internal topology > and convert it to postgis topology) > > I tried to reach grass dev several time to try to improve the postgis > export, I had no answer. That's unfortunate. > My intuition is that the slowness comes from the fact that grass tries to > write edge by edge , and each time the edge_data trigger are triggered. > The correct way would be to compute full topology structure, then > deactivate trigger, then fill table , then reactivate trigger. Or maybe it has to build the next_{left,right}_face info too. Enabling PostgreSQL logging should tell (but better not done with a ~2 million polygons topology). Oh how better it would be to speed up topology building in PostGIS :) --strk; () Free GIS & Flash consultant/developer /\ http://strk.keybit.net/services.html _______________________________________________ postgis-users mailing list [email protected] http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
