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

[Dirk (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HHH-4135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=35933#action_35933 ] 

Dirk commented on HHH-4135:
---------------------------

Glad to see that someone had finally time to look into this. However your definition took me by surprise and I cannot see any advantage in it. 

Before you reject this case you should have a look on the reference implementation. EclipseLink behaves according to the spec and I believe the definition is very "obvious". Rejecting means that you face a great performance impact when dealing with large collections. Do you have a valid use case where this non-quite-spec behavior makes sense? 

> 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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