The fix for http://opensource.atlassian.com/projects/hibernate/browse/ANN-683 in 3.3.x can cause a backward compatibility issue when upgrading from 3.2.x.

Details are in JBPAPP-1731.

An annotations-specific configuration parameter, tentatively called hibernate.legacy.foreignkey.use_identity_hashcode_to_compare, will indicate whether the identity hash code of FkSecondPass will be used by the Comparator for TreeSet<FkSecondPass>.

Setting hibernate.legacy.foreignkey.use_identity_hashcode_to_compare=true restores the 3.2.x behavior for the TreeSet<FkSecondPass> Comparator by using System.identityHashCode( fk ).

Setting hibernate.legacy.foreignkey.use_identity_hashcode_to_compare=false (the default) indicates that the 3.3.x behavior (with ANN-683 fixed) should be used.