When migration from Hibernate 5 to 6, some of our existing queries broke unexpectedly. I’ve been able to pinpoint the issue and create a reproducer, which can be found here (JIRA ticket). I’ve seen a handful of similar topics on these boards, but they all seem sufficiently different to merit starting a new discussion.
The issue occurs when modelling a many-to-many relation with three entities, using
@IdClass on the entity that represents the relation itself. A JPQL query that used to work in Hibernate 5 now throws an exception and I’ve found that removing the join fetch results in no exception being thrown, though I figure that’s more of a workaround than a solution.
I hope the reproducer is sufficient and if not, I’m more than happy to supply whatever information is needed to resolve this issue.