[postgis-users] Performance comparison between PostGIS's topology creation and topojson (the module)

[Luca Morandini]

Folks,

I am implementing a tiled-TopoJSON server in Node,js/PostGIS, and I am puzzled by 
the performance I am getting from PostGIS.

With topojson (the Node.js module), the generation of TopoJSON (the format) from a 
GeoJSON input takes about 3 seconds.... while generating a topology, for the same 
data of course, takes about 4 minutes with PostGIS.

I am probably doing something wrong; here's the code (the tiletest.orig_geometry 
table contains base geometry), please note the 0 tolerance used:

   SELECT DropTopology('tiletesttopo');
   SELECT CreateTopology('tiletesttopo', 4283);

   SELECT topology.AddTopoGeometryColumn('tiletesttopo', 'tiletest',
     'orig_geometry', 'topogeom', 'MULTIPOLYGON');

   UPDATE tiletest.orig_geometry
      SET topogeom= topology.toTopoGeom(wkb_geometry, 'tiletesttopo', 1 , 0);

Regards,

Luca Morandini
Data Architect - AURIN project
Melbourne eResearch Group
Department of Computing and Information Systems
University of Melbourne
Tel. +61 03 903 58 380
Skype: lmorandini