Comment 23 for bug 1578854

Reviewed: https://review.openstack.org/317220
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=bc3b84fb609985511510aff2aee62dbf05268b81
Submitter: Jenkins
Branch: master

commit bc3b84fb609985511510aff2aee62dbf05268b81
Author: Steve Baker <email address hidden>
Date: Sat Aug 13 15:23:08 2016 +1200

    A context cache for Resource objects

    A context cache which memoizes the resources fetched by calls to
    Resource.get_all_by_root_stack(..., cache=True)
    which are recalled by subsequent calls to Resource.get_all_by_stack.

    Because get_all_by_stack returns a collection instead of a single
    resource, there is no way of taking advantage of the SQLAlchemy
    identity map [1].

    [1] http://docs.sqlalchemy.org/en/latest/orm/session_basics.html#is-the-session-a-cache

    Change-Id: Ia5aae0c86a586041020e9798566c9e0af48c180d
    Partial-Bug: #1578854