Database downgrades do not work, no tests

[Brian Lamar]

When attempting to downgrade the Nova database using migrate's manage.py I get the following error:

http://paste.openstack.org/show/2486/

1) This error should be fixed
2) Tests should be run to ensure the database can be migrated from 1 -> X and X -> 1 (see Glance' test_migrations for a good example).

[Dan Prince (dan-prince)]

Fixing migration 031 is easy enough:

+ # grab tables
+ fixed_ips = Table('fixed_ips', meta, autoload=True)
+ virtual_interfaces = Table('virtual_interfaces', meta, autoload=True)

See the attached patch too....

However there are many other nova migrations which don't even attempt. Have a look at 030 (multi nic) which just throws an a data loss exception. I'm not sure there is always a good solution when performing the downgrades however I do agree that we should always attempt to do them.

[Gavin B (gavin-brebner-orange)]

Updating status and importance. We need upgrade/rewind to work for production clusters.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/3891

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/3891
Committed: http://github.com/openstack/nova/commit/8e825c4024f9feb18ca5e2416484ef4096c3bb06
Submitter: Jenkins
Branch: master

commit 8e825c4024f9feb18ca5e2416484ef4096c3bb06
Author: Hengqing Hu <email address hidden>
Date: Wed Feb 8 00:02:54 2012 +0800

    Make database downgrade works

    Fixes bug #854905

    Use sqlalchemy reflection whenever possible:
        http://sqlalchemy-migrate.readthedocs.org/en/latest/versioning.html

    Work around sqlalchemy-migrate sqlite 'bool column not deletable' issue:
        http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=143
        Add following sql scripts for sqlite:
            002_sqlite_downgrade.sql
            015_sqlite_downgrade.sql
            033_sqlite_downgrade.sql
            050_sqlite_downgrade.sql
            068_sqlite_downgrade.sql

    Work around sqlalchemy-migrate sqlite 'table with foreign key column not
    deletable' issue:
        http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=94
        Add following sql scripts for sqlite:
            003_sqlite_downgrade.sql
            006_sqlite_downgrade.sql
            007_sqlite_downgrade.sql
            012_sqlite_upgrade.sql
            013_sqlite_downgrade.sql
            020_sqlite_downgrade.sql
            030_sqlite_downgrade.sql
            038_sqlite_downgrade.sql
            042_sqlite_downgrade.sql
            053_sqlite_downgrade.sql
            067_sqlite_downgrade.sql

    Work around sqlalchemy-migrate 'migrate drops engine reference' issue:
        http://code.google.com/p/sqlalchemy-migrate/issues/detail?id=72

    Add following sql scripts for long primary key to work with utf-8
    mysql table:
        072_mysql_upgrade.sql

    Add following sql scripts for postgresql:
        002_postgresql_downgrade.sql

    Add snake walk test cases for database migration based on glance migration
    test.

    Change-Id: Ib454ecb4662bbf47736c1b12d9a4f969f180ceb6