[robocat]

However if the translation layer is designed for consistency, like Babelfish, it would have to replicate many of the MySQL “faults” too... e.g. it would need to have the same non-transactional DDL so it acted “correctly”!

And it would need to replicate the specialised data types like utf8mb3.

To use PostgreSQL features (such as JSON datatype) would presumably need a separate data connection and transaction, because if it isn’t implemented by MySQL, then the syntax wouldn’t be supported by Babelfish.

You would get some wins, but you don’t get a blend of the best of both.

[etaioinshrdlu]

It would be nice if it could aim for doing the sane thing over exact MySQL compatibility. But I agree it would be a minefield...