On Thu, Apr 9, 2009 at 1:15 PM, Matt Amos <[email protected]> wrote:
> 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/ <http://www.cs.umd.edu/%7Ehjs/>) which is > pretty comprehensive. Thank you, I'll order a copy. > > > cheers, > > matt >
_______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
