fields.py 文件源码

def get_db_prep_lookup(self, lookup_type, value, connection, prepared=False):
        """
        Prepare for the database lookup, and return any spatial parameters
        necessary for the query.  This includes wrapping any geometry
        parameters with a backend-specific adapter and formatting any distance
        parameters into the correct units for the coordinate system of the
        field.
        """
        # special case for isnull lookup
        if lookup_type == 'isnull':
            return []
        elif lookup_type in self.class_lookups:
            # Populating the parameters list, and wrapping the Geometry
            # with the Adapter of the spatial backend.
            if isinstance(value, (tuple, list)):
                params = [connection.ops.Adapter(value[0])]
                if self.class_lookups[lookup_type].distance:
                    # Getting the distance parameter in the units of the field.
                    params += self.get_distance(value[1:], lookup_type, connection)
                elif lookup_type in connection.ops.truncate_params:
                    # Lookup is one where SQL parameters aren't needed from the
                    # given lookup value.
                    pass
                else:
                    params += value[1:]
            elif isinstance(value, Expression):
                params = []
            else:
                params = [connection.ops.Adapter(value)]

            return params
        else:
            raise ValueError('%s is not a valid spatial lookup for %s.' %
                             (lookup_type, self.__class__.__name__))