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

[Seth Martin (JIRA)]

     [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-5855?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Seth Martin updated HHH-5855:
-----------------------------

    Attachment: CascadeMergeTest.zip

Updated test case to include Gail's suggestion.  Does not resolve bug.

> 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, 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()))

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