During a recent performance investigation it was found that flush performance in ORM 6 is worse than in ORM 5 due to a change in type profile.

Since ORM 6 marked org.hibernate.type.Type as internal, we can get rid of itable stubs though by listing concrete classes in type checks instead. This will boost performance significantly.

Hibernate JIRA: https://hibernate.atlassian.net/browse/HHH-18506