[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-4135) Merging of one-to-many relations not JPA spec compliant for lazy relations

[Emmanuel Bernard (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-4135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=36861#action_36861 ] 

Emmanuel Bernard commented on HHH-4135:
---------------------------------------

We had a team discussion on this topic today and the conclusion is that we do not violate the JPA spec but we do "violate it in spirit" but for good reasons (perf optimization and memory consumption limitation).
I have detailed the reasons on HHH-5187 as well as proposed a possible enhancement.

> Merging of one-to-many relations not JPA spec compliant for lazy relations
> --------------------------------------------------------------------------
>
>                 Key: HHH-4135
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-4135
>             Project: Hibernate Core
>          Issue Type: Bug
>          Components: entity-manager
>         Environment: Hibernate 3.2.6, Hibernate EntityManager 3.4.0, Hibernate Annotations 3.4.0, Oracle  
>            Reporter: Dirk
>         Attachments: CascadeTest.zip
>
>
> Topic has been posted to the Hibernate Forum. See https://forum.hibernate.org/viewtopic.php?f=1&t=999398
> Summary:
> Suppose you have an object Master with one-to-many relation to Detail. 
> @Entity
> public class Master implements Serializable {
>     @OneToMany(mappedBy = "master", cascade={CascadeType.MERGE, CascadeType.PERSIST})
>     private List<Detail> details = new ArrayList<Detail>();
> ...
> }
> Master is loaded without fetching Detail (= lazy) and EntityManager is closed. Master is now in detached state. Merging Master causes Hibernate EntityManager to eagerly load the Detail collection although it is in lazy state. This is not JPA spec compliant.
> JPA spec states: The persistence provider must not merge fields marked LAZY that have not been fetched: it must ignore
> such fields when merging. See 3.2.4.1 Merging Detached Entity State, p.51.
> Tested also with the latest version of EclipseLink. EclipseLink behaves as expected.
> Testcase attached (Netbeans 6.7).

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