If one believes that migrations have solved this for databases one is very sorely mistaken. Sure, you can migrate the data using some often brittle form of SQL

If one believes that migrations have solved this for databases one is very sorely mistaken. Sure, you can migrate the data using some often brittle form of SQL migration log, but this doesn't help if some code happens to be reading that table and expected the previous data shape, and this is rarely caught before the caller tries to access the data. This might be solved in some language that is some how taking full control of the data model such as an ORM, but that then pretty much breaks and additional language interoperability.