Can't pickle GeoAlchemy PostGIS objects

[danpat]

Title says it all.

If you attempt something like:

objects = session.query(MyGeoObject).all()
pickle.dumps(objects)

You'll get :

TypeError: can't pickle buffer objects

The problem is that PostGIS returns a Buffer object for geometry columns, which pickle can't handle.

A quick fix is to convert the Buffer into a string so the objects are serializable by Pickle. This does make a copy of the returned object, but I don't think that's avoidable.

This probably applies to other database that return non-pickleable types for geometry columns, and the fix is probably similar, but I don't have access to any other databases to debug on.

[danpat]

Simple patch to fix:

--- a/geoalchemy/postgis.py
+++ b/geoalchemy/postgis.py
@@ -121,6 +121,7 @@ class PGSpatialDialect(SpatialDialect):
         return PGSpatialDialect.__functions

     def process_result(self, value, type):
+        value = str(value)
         if type.wkt_internal:
             return PGPersistentSpatialElement(WKTSpatialElement(value, type.srid))
         return PGPersistentSpatialElement(WKBSpatialElement(value, type.srid))

[elemoine]

This fix breaks the tests. I had to revert d7850ca. See ebcdb37.

[karankurani]

I have the same problem while using pylibmc to cache objects which have geometry columns. The pylibmc library uses pickle internally to serialize/deserialize objects.