Comment 13 for bug 1757966

Reviewed: https://review.openstack.org/564717
Committed: https://git.openstack.org/cgit/openstack/mistral/commit/?id=f2a9bd45abf0b08e1a906faf29e4a85579d1ba0b
Submitter: Zuul
Branch: master

commit f2a9bd45abf0b08e1a906faf29e4a85579d1ba0b
Author: Renat Akhmerov <email address hidden>
Date: Fri Apr 27 17:01:31 2018 +0700

    Do not copy workflow environment into subworkflows

    * We previously always copied a workflow environment of a parent
      workflow into a subworkflow when starting it. However, this is
      redundant because we now have 'root_execution_id' field in the
      the workflow execution model so that we can always get an
      environment of a subworkflow just by accessing the root execution.
      It saves a lot of space in DB and increases performance in cases
      when we have a large workflow environment and many subworkflows.

    Related-Bug: #1757966
    Change-Id: I15077240ba53663a6267b886ab7b081a7dde2710