util.py 文件源码

def with_parent(instance, prop):
    """Create filtering criterion that relates this query's primary entity
    to the given related instance, using established :func:`.relationship()`
    configuration.

    The SQL rendered is the same as that rendered when a lazy loader
    would fire off from the given parent on that attribute, meaning
    that the appropriate state is taken from the parent object in
    Python without the need to render joins to the parent table
    in the rendered statement.

    .. versionchanged:: 0.6.4
        This method accepts parent instances in all
        persistence states, including transient, persistent, and detached.
        Only the requisite primary key/foreign key attributes need to
        be populated.  Previous versions didn't work with transient
        instances.

    :param instance:
      An instance which has some :func:`.relationship`.

    :param property:
      String property name, or class-bound attribute, which indicates
      what relationship from the instance should be used to reconcile the
      parent/child relationship.

    """
    if isinstance(prop, util.string_types):
        mapper = object_mapper(instance)
        prop = getattr(mapper.class_, prop).property
    elif isinstance(prop, attributes.QueryableAttribute):
        prop = prop.property

    return prop._with_parent(instance)