functions.py 文件源码

def as_postgresql(self, compiler, connection):
        geo_field = GeometryField(srid=self.srid)  # Fake field to get SRID info
        src_field = self.get_source_fields()[0]
        geography = src_field.geography and self.srid == 4326
        if geography:
            # Set parameters as geography if base field is geography
            for pos, expr in enumerate(
                    self.source_expressions[self.geom_param_pos + 1:], start=self.geom_param_pos + 1):
                if isinstance(expr, GeomValue):
                    expr.geography = True
        elif geo_field.geodetic(connection):
            # Geometry fields with geodetic (lon/lat) coordinates need special distance functions
            if self.spheroid:
                self.function = 'ST_Distance_Spheroid'  # More accurate, resource intensive
                # Replace boolean param by the real spheroid of the base field
                self.source_expressions[2] = Value(geo_field._spheroid)
            else:
                self.function = 'ST_Distance_Sphere'
        return super(Distance, self).as_sql(compiler, connection)