[hibernate-issues] [Hibernate-JIRA] Created: (HHH-3642) EJB3 inheritance strategy TABLE_PER_CLASS does not work on HSQLDB

[Wolfgang Knauf (JIRA)]

EJB3 inheritance strategy TABLE_PER_CLASS does not work on HSQLDB
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                 Key: HHH-3642
                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-3642
             Project: Hibernate Core
          Issue Type: Bug
    Affects Versions: 3.3.1
         Environment: JBoss 5.0GA, Java 1.6, Hypersonic 1.8.0.8
            Reporter: Wolfgang Knauf
         Attachments: InheritanceTablePerClass.ear

I use an EJB3 entity bean with inheritance strategy "TABLE_PER_CLASS":

@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public abstract class Base implements Serializable
{
   ...

When loading a list of base classes, all subclass fields are null. The union subclause in the query does not work on HSQLDB. 

Attached is a full EJB sample, runnable on JBoss 4.2/5.0 (project export of Eclipse 3.4/WebTools 3.0 with sources). After deploying, it can be tested by browsing to http://localhost:8080/InheritanceTablePerClassWeb/
See this output:
...
Loading ALL
Item: Child 1, child field 1: null
Item: Child 2, child field 2: null
Item: Child 3, child field 3: Field of Child3
...
Here, all childs are loaded. The fields of type "Child1" and "Child2" are null, fields of type "Child3" are filled.


This is probably a duplicate of http://opensource.atlassian.com/projects/hibernate/browse/HHH-2920
The described workaround to change all NULL expressions to "cast (null as VARCHAR)" results in a working query, but I see no chance to pre-configure this query in the entity manager.

I created another bug, because the impact is different (it breaks a feature of EJB3), and so I consider severity to be higher.

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