Note that the main problem here is how collections are modeled in terms of OuterJoinableAssociation instances. A "basic collection" results in one OuterJoinableAssociation generated. However, one-to-many and many-to-many collections result in 2 OuterJoinableAssociation instances generated; the first represents the collection itself (mainly the "collection key"), the second represents the associated entity. And in the case of Maps, that could even be 3 OuterJoinableAssociation instances (one for the collection, one for the value, one for the key)!