On Thu, Apr 9, 2009 at 12:36 AM, Frederik Ramm <[email protected]> wrote: > pablo platt wrote: >> It uses B-Tree index so the only way I know to enable spatial index is to >> use space-filling-curves (z-order, morton codes) > > I've not come across these terms but from your references it seems that > this is very much the same as our "Quadtiles" approach. The OSM db is > still based on MySQL which has no multi-dimensional indexes either
mysql has had a spatial index type (R-Tree) since version 4.1, but only for myisam tables which means no transactions or foreign keys :-( >> Using z-order >> with B-Tree seem simpler and supported out of the box >> by most databases. > > I don't think that the PostGIS developers cared about what was supported > by other databases. as marcus has pointed out the performance of 1-d indexes for 2-d data is often poor. for further reading i recommend "Foundations of Multidimensional and Metric Data Structures" by H. Samet (http://www.cs.umd.edu/~hjs/) which is pretty comprehensive. cheers, matt _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
