Subselect not used when batch loading by id in Hibernate

Issue

• An entity class is batch enabled and is using SUBSELECT fetch.

  @Entity
  @BatchSize(size = 1000)
  public class EmployeeGroupSubselect {
      ...
      @OneToMany(cascade = CascadeType.ALL)
      @Fetch(FetchMode.SUBSELECT)
      private List<Employee> employees = new ArrayList<Employee>();
      ....
  }
  

• When fetching a set of entities and their associations, subselect is not used to fetch the associations.

• For each entity, a separate query is issue to fetch the association

  select
      employees0_.EmployeeGroupSubselect_departmentName as Employee1_3_0_,
      employees0_.EmployeeGroupSubselect_groupName as Employee2_3_0_,
      employees0_.employees_id as employee3_3_0_,
      employee1_.id as id1_1_1_,
      employee1_.name as name2_1_1_ 
  from
      EmployeeGroupSubselect_Employee employees0_ 
  inner join
      Employee employee1_ 
          on employees0_.employees_id=employee1_.id 
  where
      employees0_.EmployeeGroupSubselect_departmentName=? 
      and employees0_.EmployeeGroupSubselect_groupName=?