Comment 8 for bug 1744948

Reviewed: https://review.openstack.org/536869
Committed: https://git.openstack.org/cgit/openstack/keystone/commit/?id=59b1aacdbaba72df62167793ea2b3ed2ba5b303f
Submitter: Zuul
Branch: master

commit 59b1aacdbaba72df62167793ea2b3ed2ba5b303f
Author: Colleen Murphy <email address hidden>
Date: Tue Jan 23 16:36:15 2018 +0100

    Fix column rename migration for mariadb 10.2

    MariaDB 10.2 introduced an issue where an automatic check constraint is
    applied to boolean columns and is not automatically updated on a column
    rename alter operation[1]. A similar issue preventing dropping such a
    column was already fixed[2], so this patch changes the migration to drop
    and readd the column instead of attempting a column rename.

    Unfortunately since the mistake was already made, it is possible for
    deployments out in the wild to have made it past the expand step and be
    currently stuck in the contract step. To accomodate them, we add the new
    column as part of the contract step if necessary. Again, since there
    should be no data in this table, we don't need to worry about online
    upgrades here.

    [1] https://jira.mariadb.org/browse/MDEV-13508
    [2] https://jira.mariadb.org/browse/MDEV-11114

    Change-Id: Icbd58464182b082854fb5d73ccc93c900ede020c
    Closes-bug: #1744948