--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/web/lib/django/contrib/gis/db/models/sql/where.py	Wed Jun 02 18:57:35 2010 +0200
@@ -0,0 +1,89 @@
+from django.db.models.fields import Field, FieldDoesNotExist
+from django.db.models.sql.constants import LOOKUP_SEP
+from django.db.models.sql.expressions import SQLEvaluator
+from django.db.models.sql.where import Constraint, WhereNode
+from django.contrib.gis.db.models.fields import GeometryField
+
+class GeoConstraint(Constraint):
+    """
+    This subclass overrides `process` to better handle geographic SQL
+    construction.
+    """
+    def __init__(self, init_constraint):
+        self.alias = init_constraint.alias
+        self.col = init_constraint.col
+        self.field = init_constraint.field
+
+    def process(self, lookup_type, value, connection):
+        if isinstance(value, SQLEvaluator):
+            # Make sure the F Expression destination field exists, and
+            # set an `srid` attribute with the same as that of the
+            # destination.
+            geo_fld = GeoWhereNode._check_geo_field(value.opts, value.expression.name)
+            if not geo_fld:
+                raise ValueError('No geographic field found in expression.')
+            value.srid = geo_fld.srid
+        db_type = self.field.db_type(connection=connection)
+        params = self.field.get_db_prep_lookup(lookup_type, value, connection=connection)
+        return (self.alias, self.col, db_type), params
+
+class GeoWhereNode(WhereNode):
+    """
+    Used to represent the SQL where-clause for spatial databases --
+    these are tied to the GeoQuery class that created it.
+    """
+    def add(self, data, connector):
+        if isinstance(data, (list, tuple)):
+            obj, lookup_type, value = data
+            if ( isinstance(obj, Constraint) and
+                 isinstance(obj.field, GeometryField) ):
+                data = (GeoConstraint(obj), lookup_type, value)
+        super(GeoWhereNode, self).add(data, connector)
+
+    def make_atom(self, child, qn, connection):
+        lvalue, lookup_type, value_annot, params_or_value = child
+        if isinstance(lvalue, GeoConstraint):
+            data, params = lvalue.process(lookup_type, params_or_value, connection)
+            spatial_sql = connection.ops.spatial_lookup_sql(data, lookup_type, params_or_value, lvalue.field, qn)
+            return spatial_sql, params
+        else:
+            return super(GeoWhereNode, self).make_atom(child, qn, connection)
+
+    @classmethod
+    def _check_geo_field(cls, opts, lookup):
+        """
+        Utility for checking the given lookup with the given model options.
+        The lookup is a string either specifying the geographic field, e.g.
+        'point, 'the_geom', or a related lookup on a geographic field like
+        'address__point'.
+
+        If a GeometryField exists according to the given lookup on the model
+        options, it will be returned.  Otherwise returns None.
+        """
+        # This takes into account the situation where the lookup is a
+        # lookup to a related geographic field, e.g., 'address__point'.
+        field_list = lookup.split(LOOKUP_SEP)
+
+        # Reversing so list operates like a queue of related lookups,
+        # and popping the top lookup.
+        field_list.reverse()
+        fld_name = field_list.pop()
+
+        try:
+            geo_fld = opts.get_field(fld_name)
+            # If the field list is still around, then it means that the
+            # lookup was for a geometry field across a relationship --
+            # thus we keep on getting the related model options and the
+            # model field associated with the next field in the list
+            # until there's no more left.
+            while len(field_list):
+                opts = geo_fld.rel.to._meta
+                geo_fld = opts.get_field(field_list.pop())
+        except (FieldDoesNotExist, AttributeError):
+            return False
+
+        # Finally, make sure we got a Geographic field and return.
+        if isinstance(geo_fld, GeometryField):
+            return geo_fld
+        else:
+            return False