SQL Migrations are the accepted method for OpenStack projects to ensure that a given schema is consistent across deployments. Often these migrations include updating of the underlying data as well as modifications to the schema. It is inadvisable to perform a downwards migration in any environment.
Best practices state: when reverting post schema migration the correct course is to restore to a known-good state of the database.
Many migrations in OpenStack include data-manipulation to ensure the data conforms to the new schema; often these data-migrations are difficult or impossible to reverse without significant overhead. Performing a downgrade of the schema with such data manipulation can lead to inconsistent or broken state. The possibility of bad-states, relatively minimal testing, and no demand for support renders a downgrade of the schema an unsafe action.
The proposed change is as follows:
Downgrade paths can continue to be supported.
Morgan Fainberg (irc: morganfainberg) Matt Fischer (irc: mfisch)
No external dependencies.
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