Comment 2 for bug 1921981

Reviewed: https://review.opendev.org/c/openstack/tacker/+/830146
Committed: https://opendev.org/openstack/tacker/commit/75778a2d98e1440f56f2378798062133f57b5568
Submitter: "Zuul (22348)"
Branch: master

commit 75778a2d98e1440f56f2378798062133f57b5568
Author: Hiromu Asahina <email address hidden>
Date: Mon Feb 21 11:03:33 2022 +0000

    Suppress Warnings for SQL Alchemy

    The ``cache_ok`` attribute for SQL Alchemy TypeDecorator will emit a
    warning when its value is set to the default value ``None``. When this
    value is set to True, SQL Alchemy will cache SQL query and reuse it
    later when the same query is called again, and vice versa.

    This patch simply sets ``cache_ok`` to TypeDecorator classes according
    to whether it can be used as a cache key or not [1].

    [1] https://docs.sqlalchemy.org/en/14/core/type_api.html#sqlalchemy.types.ExternalType.cache_ok

    Closes-Bug: #1921981
    Change-Id: I503c93d6e8869b30c49909c95fb2669862d28a3f