I have employee and employeedetail classes mapped using primary key join column (employee_id) (bi directional)





@Entity
@Table(name="employee")
public class Employee {

@Id
@GeneratedValue
@Column(name="employee_id")
private Long employeeId;

@Column(name="firstname")
private String firstname;

@Column(name="lastname")
private String lastname;

@Column(name="birth_date")
@Temporal(value = TemporalType.DATE )
private Date birthDate;

@Column(name="cell_phone")
private String cellphone;

@OneToOne(mappedBy="empl", cascade=CascadeType.ALL)
private EmployeeDetail employeeDetail;

...
}


@Table(name="employeedetail")
public class EmployeeDetail {


@Id
@Column(name="employee_id", unique=true, nullable=false)
@GeneratedValue(generator="gen")
@GenericGenerator(name="gen", strategy="foreign", parameters=@Parameter(name="property", value="empl"))
private Long employeeId;

@Column(name="street")
private String street;

@Column(name="city")
private String city;

@Column(name="state")
private String state;

@Column(name="country")
private String country;

@OneToOne
@PrimaryKeyJoinColumn
private Employee empl;
....................
}

Can someone please clarify why when executing the following query session.createQuery("from Employee").list();

A) the join queries like 2),3) and 4) get executed to fetch data from employeedetail?
why not directly fetch from employeedetail table using the employeeid value in employee object without a join?



1) Hibernate: select employee0_.employee_id as employee1_0_, employee0_.birth_date as birth_da2_0_, employee0_.cell_phone as cell_pho3_0_, employee0_.firstname as firstnam4_0_, employee0_.lastname as lastname5_0_ from employee employee0_

2) Hibernate: select employeede0_.employee_id as employee1_1_0_, employeede0_.city as city2_1_0_, employeede0_.country as country3_1_0_, employeede0_.state as state4_1_0_, employeede0_.street as street5_1_0_, employee1_.employee_id as employee1_0_1_, employee1_.birth_date as birth_da2_0_1_, employee1_.cell_phone as cell_pho3_0_1_, employee1_.firstname as firstnam4_0_1_, employee1_.lastname as lastname5_0_1_ from employeedetail employeede0_ left outer join employee employee1_ on employeede0_.employee_id=employee1_.employee_id where employeede0_.employee_id=?
3) Hibernate: select employeede0_.employee_id as employee1_1_0_, employeede0_.city as city2_1_0_, employeede0_.country as country3_1_0_, employeede0_.state as state4_1_0_, employeede0_.street as street5_1_0_, employee1_.employee_id as employee1_0_1_, employee1_.birth_date as birth_da2_0_1_, employee1_.cell_phone as cell_pho3_0_1_, employee1_.firstname as firstnam4_0_1_, employee1_.lastname as lastname5_0_1_ from employeedetail employeede0_ left outer join employee employee1_ on employeede0_.employee_id=employee1_.employee_id where employeede0_.employee_id=?
4) Hibernate: select employeede0_.employee_id as employee1_1_0_, employeede0_.city as city2_1_0_, employeede0_.country as country3_1_0_, employeede0_.state as state4_1_0_, employeede0_.street as street5_1_0_, employee1_.employee_id as employee1_0_1_, employee1_.birth_date as birth_da2_0_1_, employee1_.cell_phone as cell_pho3_0_1_, employee1_.firstname as firstnam4_0_1_, employee1_.lastname as lastname5_0_1_ from employeedetail employeede0_ left outer join employee employee1_ on employeede0_.employee_id=employee1_.employee_id where employeede0_.employee_id=?


B) also, for the query session.createQuery("from EmployeeDetail").list();

why employee info is fetched as per below select queries instead of being proxied?


Hibernate: select employeede0_.employee_id as employee1_1_, employeede0_.city as city2_1_, employeede0_.country as country3_1_, employeede0_.state as state4_1_, employeede0_.street as street5_1_ from employeedetail employeede0_

Hibernate: select employee0_.employee_id as employee1_0_0_, employee0_.birth_date as birth_da2_0_0_, employee0_.cell_phone as cell_pho3_0_0_, employee0_.firstname as firstnam4_0_0_, employee0_.lastname as lastname5_0_0_ from employee employee0_ where employee0_.employee_id=?
Hibernate: select employee0_.employee_id as employee1_0_0_, employee0_.birth_date as birth_da2_0_0_, employee0_.cell_phone as cell_pho3_0_0_, employee0_.firstname as firstnam4_0_0_, employee0_.lastname as lastname5_0_0_ from employee employee0_ where employee0_.employee_id=?
Hibernate: select employee0_.employee_id as employee1_0_0_, employee0_.birth_date as birth_da2_0_0_, employee0_.cell_phone as cell_pho3_0_0_, employee0_.firstname as firstnam4_0_0_, employee0_.lastname as lastname5_0_0_ from employee employee0_ where employee0_.employee_id=?