How do I stop IN CLAUSE when query a hierarchy of object.

Question

I have a base class which is annotated with
@Entity(name="UdmHierarchyObject")
@Table(name="UDM_HIERARCHIES")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
public class UdmHierarchyObject ...
I have a single table hierarchy of objects which use the following annotation:
@Entity(name="Lookup")
@DiscriminatorValue(value="Lookup")
public class Lookup extends UdmHierarchyObject ....
Now I may have MANY classes that extend the base and this is were I am worried. When I query, EclipseLink always creates an IN CLAUSE including all the subclassed entities, which I don't really need. And I worry about it's size.
An example query produces the SELECT below.
select l from Lookup l join l.data d
where l.hierarchyObjectName = :name and d.name = 'Code'
order by d.value"
2008-05-28 14:06:31,773 DEBUG [oracle.toplink.sql:135] - ClientSession(22145060)--Connection(23069842)--
SELECT t1.ID, t1.JPA_DISC, t1.OBJECT_NAME, t1.OBJECT_TYPE, t1.UPDATED_ON, t2.ID, t2.HIERARCHY_NAME, t2.PARENT_ID, t2.REFERENCE_ID FROM UDM_DATA t0, UDM_HIERARCHIES t2, UDM_OBJECTS t1 WHERE (((((t2.HIERARCHY_NAME = ?) AND (t0.DATA_NAME = ?)) AND (t2.ID = t1.ID)) AND (t1.JPA_DISC IN (?, ?))) AND (t0.OWNER_ID = t1.ID)) ORDER BY t0.DATA_VALUE ASC
bind => [StateCode, Code, Lookup, EventTypeCode]
The actual query is fine, however I don't always need the t1.JPA_DISC IN (?, ?) part because I am providing sufficient filtering.
Is there a way to suppress this in the query, or should I not be bothered with a large IN CLAUSE?
You comments would be appreciated.

Answer 1

The issue is you are querying a branch class, so only the children of this branch must be filtered. Unless you are noticing real performance issues with the IN, I would not worry about it too much.
Otherwise, you could consider using joined inheritance, or some level in between joined and single table (JPA does not support this, but TopLink does if you customize your descriptors).
You could also customize your TopLink descriptors using a DescriptorCustomizer to change how subclasses are filtered. You would need to set the ClassDescriptor's InheritancePolicy's withAllSubclassesExpression.
-- James : http://www.eclipselink.org