Specifically.. ok, nothing prevents a parameter from being composite. But nothing says that should be supported either.

There are just a lot of difficulties in implementing this properly.

In regards to named parameters, my intent was to not use named params on the JDBC side in various cases, even though named parameters were used on the Hibernate/JPA side. - they do not have to correlate. EVen if we were to support composite param types, I would then expect them to fall into this bucket.