Comment 14 for bug 1494108

Reviewed: https://review.openstack.org/232675
Committed: https://git.openstack.org/cgit/openstack/heat/commit/?id=9ee5d625ebcc8124170c8b269e0d20664fe286c3
Submitter: Jenkins
Branch: stable/juno

commit 9ee5d625ebcc8124170c8b269e0d20664fe286c3
Author: Steve Baker <email address hidden>
Date: Fri Sep 18 11:56:57 2015 +1200

    Only write to template files if template data changes

    Currently the template data is assigned to the files dict regardless
    of whether the data has changed or not.

    This has no consequence on Liberty, but the files dict in Kilo
    and Juno is a sqlalchemy MutableDict so these assignments are triggering
    updates to the raw_template table. These updates are even triggered for
    calls to heat resource-list. With large raw_template records this can make
    heat unusable.

    Therefore this fix is presented here as having no effect (and being
    harmless) to git master, but high priority backports for Kilo and Juno.

    Change-Id: Ibb714a9c5dc9f6879ff108419127da985a57897b
    Closes-Bug: #1494108
    (cherry-picked from 779ba8e431aecac3c451c08aedcc0ad8cf0a4449)