While migrating to the latest version of Hibernate, we have discovered an issue with how queries are generated for parent-child relations within the same table.

Here is a simple example, we have an entity that may point to itself to provide a parent-child relation:

@Entity
@Table(name = "subpart")
public class SchedulingSubpart {
private Long id;
private SchedulingSubpart parentSubpart;

@Id
@Column(name = "id")
public Long getId()

public void setId(Long id)

@ManyToOne(optional = true)
@JoinColumn(name = "parent")
public SchedulingSubpart getParentSubpart()

public void setParentSubpart(SchedulingSubpart parentSubpart)

}

For the following HQL
select s.id, p.id from SchedulingSubpart s inner join s.parentSubpart p

generates the following SQL
select
s1_0.id
from
subpart s1_0
join
subpart p1_0
on p1_0.id=s1_0.parent

And returning the same id for the subpart and its parent (p1_0.id is not returned).

See SchedulingSubpart.java ORMStandaloneTestCase.java for more details.