You'll also have to go back to your changes in https://hibernate.onjira.com/browse/HHH-7579 Those are bogus, too. Just as Hsqldb is now broken (see: https://hibernate.onjira.com/browse/HHH-7785), Oracle (at least 10g and later) is broken too, as it supports 'not null unique' without any trouble.
You'll also have to go back to your changes in https://hibernate.onjira.com/browse/HHH-7579
Those are bogus, too. Just as Hsqldb is now broken (see: https://hibernate.onjira.com/browse/HHH-7785),
Oracle (at least 10g and later) is broken too, as it supports 'not null unique' without any trouble.