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* Ported to SQLAlchemy 0.6
* When fetching objects of mapped classes, the geometry column
is queried in WKB.
* The WKB value of a geometry column can be accessed directly,
without making a new database query, using the attribute
geom_wkb (for example: s.the_geom.geom_wkb).
* Introduced DBSpatialElement that can be used to wrap the
result of a database function, that returned a new geometry, so
that new queries can be executed on the result.
>>> buffer_geom = DBSpatialElement(session.scalar(r.geom.buffer(10.0)))
>>> session.scalar(buffer_geom.wkt)
* Removed 'SFS' flag for GeometryColumn.
* When using database specific functions on geometry columns
(Spot.geom.kml, but not s.geom.kml!), a comparator has to be set
manually when defining the mapping.
* Updated documentation and examples.
* Use spatial index for Spatialite.
* Set NOT NULL constraints in database (nullable=False).
* GeometryBase: changed default value of dimension to 2.