[ZMapServer-Developers] PCL: MapServer-specific datastore committed to CVS

[Sean G. <sgi...@fr...>]

As I mentioned in a previous email, the GEOS software that I would like 
to use for evaluation of spatial predicates ("intersects", "contains", 
etc) resists compilation on windows with MSVC6.  This means that PCL 
users on windows will not be able to use GEOS until they upgrade to 
Python 2.4.  2.4 binaries should be compiled using the next higher 
version of the MS compiler.  As far as I know, there is not a stable 
Zope release that is perfectly compatible with Python 2.4 ... which 
leaves a gap to bridge.

As a bridge, I've committed a new data store and filtering iterator to 
PCL's engine.mapserver.data module that operate without any dependency 
on GEOS.  Unfortunately, MapServer's own geometry operations are 
limited to "intersects".  Usage is like this (from the tests):

     from cartography.engine.mapserver.data import DiskFeatureStore
     from cartography.data import Query
     from cartography.filter import PythonFilter
     from cartography.spatial import Point

     subject_p = Point(0.0, 51.5)
     pyfilt = PythonFilter('g.intersects(p)')
     query = Query(filter=pyfilt, p=subject_p)
     features = [f for f in self.features(query)]
     assert len(features) == 1, len(features)

Etienne, it is not as fast as a query using mapscript, but a loss of 
speed is the price we pay now for the richer and more powerful filter 
expressions.  If you have access to the MSVC6 compiler. you may want to 
check out the latest PCL from CVS and give it a try.

I'm going to be out of the office through Saturday, catch up with you 
then.

cheers,
Sean

--
Sean Gillies
sgillies at frii dot com
http://users.frii.com/sgillies