[MariaDB developers] Re: Proposal: mariadbd should automatically upgrade system tables and data directory on startup

Having an internal schema version that would be incremented only on internal tables schema changes (and not linked to major/minor versioning of MariaDB) in addition to per-storage data format versions would allow a relatively safe downgrade even between major versions if there has been no changes of internal schemas and of data format of the currently used storage plugins. It would make it easy to block the execution of MariaDB only if one of the structure is newer than the server expects and it could be bypassed with a startup variable forcing the execution even if the schemas and/or data format might not be compatible.