jakobjoachim / StreamEntityGraphBug

When using an EntityGraph and a stream query, the entities contained in the root entity need to be returned by the SQL in adjacent rows. When this is not the case (for example by using orderBy) the repository call will return one result for each line in the resulting SQL Example:

@Entity
public class SomeEntity {
	@Id
	private Integer id;

	@OneToMany
	@OrderBy
	private List<AnotherEntity> someOrderedValues;

       ...
}

@Entity
public class AnotherEntity {
	@Id
  	private Integer id;

	public AnotherEntity() {
	}

	...
}

We have two Objects in the database (H2, JSON just for ease of overview):

{
    "id": 5,
    "someOrderedValue": [{
         "id": 1
    }, {
         "id": 3
    }]
}

{
    "id": 6,
    "someOrderedValue": [{
         "id": 2
    }, {
         "id": 4
    }]
}

When we call the repository the SQL will look something like this:

select someentity0_.id                     as id1_1_0_,
       anotherent2_.id                     as id1_0_1_,
       someordere1_.some_entity_id         as some_ent1_2_0__,
       someordere1_.some_ordered_values_id as some_ord2_2_0__
from some_entity someentity0_
         left outer join some_entity_some_ordered_values someordere1_
                         on someentity0_.id = someordere1_.some_entity_id
         left outer join another_entity anotherent2_
                         on someordere1_.some_ordered_values_id = anotherent2_.id
where someentity0_.id in (5, 6)
order by anotherent2_.id asc

Resulting in the following:

	someentity0_.id	anotherent2_.id	someordere1_.some_entity_id	someordere1_.some_ordered_values_id
1	5	1	5	1
2	6	2	6	2
3	5	3	5	3
4	6	4	6	4

Because we are streaming the results we get 4 results (one for each line) because as soon as the cursor finds a new entity it will return the current one. When a groupById is added to the Repository method everything will work correctly (line 2 and 3 are swapped in the table). When using List instead of Stream in the Repository Method everything will work correctly as well.

This problem is present when using Stream + EntityGraph in situations where the SQL doesn't return the entities in adjacent rows.

The bug report is here: https://hibernate.atlassian.net/browse/HHH-14527