[evanelias]

This is solved more cleanly in declarative schema management systems, where you have a schema repo of CREATE statements, and the tool can auto-generate the correct DDL. You never need to write any migrations at all, up or down. If you need to roll back, you use `git revert` and then auto-generate from there. The history is in Git, and you can fully leverage Git like a proper codebase.

A key component is that the schema management tool must be able to detect and warn/error on destructive changes -- regardless of whether it's a conceptual revert or just a bad change (i.e. altering a column's data type in a lossy way). My declarative tool Skeema [1] has handled this since the first release, among many other safety features.

That all said, schema changes are mostly orthogonal to database version upgrades, so this whole subthread is a bit different than the issue discussed several levels above :) The root of the blue/green no-rollback-after-upgrade issue discussed above is that MySQL logical replication officially supports older-version-primary -> newer-version-replica, but not vice versa. Across different release series, the replication format can change in ways that the older version replicas do not understand or support.

[1] https://github.com/skeema/skeema