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"""A naive example illustrating techniques to help
embed PostGIS functionality.
This example was originally developed in the hopes that it would be extrapolated into a comprehensive PostGIS integration layer. We are pleased to announce that this has come to fruition as `GeoAlchemy <http://www.geoalchemy.org/>`_.
The example illustrates:
* a DDL extension which allows CREATE/DROP to work in
conjunction with AddGeometryColumn/DropGeometryColumn
* a Geometry type, as well as a few subtypes, which
convert result row values to a GIS-aware object,
and also integrates with the DDL extension.
* a GIS-aware object which stores a raw geometry value
and provides a factory for functions such as AsText().
* an ORM comparator which can override standard column
methods on mapped objects to produce GIS operators.
* an attribute event listener that intercepts strings
and converts to GeomFromText().
* a standalone operator example.
The implementation is limited to only public, well known
and simple to use extension points.
E.g.::
print session.query(Road).filter(Road.road_geom.intersects(r1.road_geom)).all()
"""
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