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This looks more complicated than it is, but it's really quite simple. Essentially we have to deal with two possible configurations: - For existing deployments, the DB sync operation should apply any outstanding sqlalchemy-migrate-based migrations, dummy apply the initial alembic migration, and then apply any additional alembic-based migrations requested (or any available, if no version is specified). - For new deployments, the DB sync operation should apply the initial alembic migration and any additional alembic-based migrations requested (or any available, if no version is specified). No sqlalchemy-migrate-based migrations will ever be applied. While we continue to allow users to request a specific database migration version to upgrade to, we *do not* allow them to request a sqlalchemy-migrate-based migration version. There's no good reason to do this - the deployment won't run with an out-of-date DB schema (something that's also true of the alembic migration, fwiw) - and we want to get people off of sqlalchemy-migrate as fast as possible. A change in a future release can remove the sqlalchemy-migrate-based migrations once we're sure that they'll have upgraded to a release including all of the sqlalchemy-migrated-based migrations (so Wallaby). Tests are modified to validate the sanity of these operations. They're mostly trivial changes, but we do need to do some funky things to ensure that (a) we don't use logger configuration from 'alembic.ini' that will mess with our existing logger configuration and (b) we re-use connection objects as necessary to allow us to run tests against in-memory databases, where a different connection would actually mean a different database. We also can't rely on 'WalkVersionsMixin' from oslo.db since that only supports sqlalchemy-migrate [1]. We instead must re-invent the wheel here somewhat. [1] https://github.com/openstack/oslo.db/blob/10.0.0/oslo_db/sqlalchemy/test_migrations.py#L42-L44 Change-Id: I850af601f81bd5d2ecc029682ae10d3a07c936ce Signed-off-by: Stephen Finucane <stephenfin@redhat.com>
26 lines
1.3 KiB
YAML
26 lines
1.3 KiB
YAML
---
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upgrade:
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- |
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The database migration engine has changed from `sqlalchemy-migrate`__ to
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`alembic`__. For most deployments, this should have minimal to no impact
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and the switch should be mostly transparent. The main user-facing impact is
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the change in schema versioning. While sqlalchemy-migrate used a linear,
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integer-based versioning scheme, which required placeholder migrations to
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allow for potential migration backports, alembic uses a distributed version
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control-like schema where a migration's ancestor is encoded in the file and
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branches are possible. The alembic migration files therefore use a
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arbitrary UUID-like naming scheme and the ``nova-manage db sync`` and
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``nova-manage api_db sync`` commands now expect such an version when
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manually specifying the version that should be applied. For example::
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$ nova-manage db sync 8f2f1571d55b
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It is no longer possible to specify an sqlalchemy-migrate-based version.
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When the ``nova-manage db sync`` and ``nova-manage api_db sync`` commands
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are run, all remaining sqlalchemy-migrate-based migrations will be
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automatically applied. Attempting to specify an sqlalchemy-migrate-based
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version will result in an error.
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.. __: https://sqlalchemy-migrate.readthedocs.io/en/latest/
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.. __: https://alembic.sqlalchemy.org/en/latest/
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