I have a class extending an existing entity with single table strategy (which I can\'t change). I want to use UniqueConstraint for that entity so I tried:
@E
You cannot override the base class @Table declaration, that's why the sub-class uniqueConstraints directive is ignored.
With JPA you can override annotations with xml declarations. So you need to add an orm.xml file in your class-pat and add the unique constraints there:
...
first_column
second_column
This way you might not even need the MyDocument sub-class, if you only used it to override the DDL schema.