[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-5855) The method "merge" from the EntityManager causes a duplicated "insert" of a child entity.

The method "merge" from the EntityManager causes a duplicated "insert" of a child entity. ----------------------------------------------------------------------------------------- Key: HHH-5855 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-5855 Project: Hibernate Core Issue Type: Bug Components: annotations, core, entity-manager Affects Versions: 3.3.1, 3.6.0 Environment: Hibernate-Core 3.6.0, Hibernate EntityManager 3.6.0, Derby, Spring 3.0.5 (Configuration), JUnit 4.5 Reporter: Seth Martin Priority: Critical Attachments: CascadeMergeTest.zip The method "merge" from the EntityManager causes a duplicated "insert" of a child entity. Related to HHH-3332 h3.Observed Behavior: When you have an Entity A with a OneToMany(fetch=LAZY, cascade=ALL or (MERGE and PERSIST)) relationship to another Entity B and attempt to add an new B instance to A hibernate will generate a duplicate insert command upon commit. I have witnessed this problem occurring when this procedure is followed: # retrieve an instance of A from persistence (A a = em.find(A.class, id)) # add a new B to A (a.getBs.add(new B())) # merge instance 'a' back into persistence (em.merge(a)) Upon transaction commit hibernate will generate an additional "insert" statement and insert the new instance of b into the data source twice. h3.Expected behavior: I would expect hibernate to only perform a single insertion when 'a' is merged back to persistence and the B's are created through the cascade. h3.Notes (Discoveries): This problem can be worked around by: * Changing the OneToMany relationship from a List to a Set * Only using either Cascade MERGE or PERSIST not both of ALL * Add a new B to A.getBs by adding to the '0' index (a.getBs.add(0,new B()))