Why doesn't Eclipselink generate the ON DELETE CASCADE clause in a unidirectional #ManyToOne relationship? - jpa

Question

These are two related entities in Eclipselink JPA:
#Entity
public class Department {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
}
#Entity
public class Person {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String firstName;
private String lastName;
#ManyToOne(cascade={CascadeType.ALL})
private Department department;
}
and this is the generated DDL:
CREATE TABLE PERSON (ID BIGINT IDENTITY NOT NULL, FIRSTNAME VARCHAR, LASTNAME VARCHAR, DEPARTMENT_ID BIGINT, PRIMARY KEY (ID))
CREATE TABLE DEPARTMENT (ID BIGINT IDENTITY NOT NULL, NAME VARCHAR, PRIMARY KEY (ID))
ALTER TABLE PERSON ADD CONSTRAINT FK_PERSON_DEPARTMENT_ID FOREIGN KEY (DEPARTMENT_ID) REFERENCES DEPARTMENT (ID)
The environment is:
- eclipselink 2.5.2
- mysql-connector-java 5.1.6
I would expect to have at least a ON DELETE CASCADE clause on the foreign key definition.
What is the cascade option intended for, in the #ManyToOne relationship?
Do I really have to delete the children records manually before deleting the parent record?

Answer 1

The CascadeType you mention in your example is one value of those: ALL, PERSIST, MERGE, REMOVE, REFRESH, DETACH. This is ORM, but not SQL DDL related.
I guess You are searching for a SQL DDL foreign key constraint definition ...on delete cascade. To geht this SQL DDL generated, You need an #CascadeOnDelete annotation, as shown in this example:
...
#OneToMany(mappedBy="abc", orphanRemoval=true, cascade={CascadeType.ALL})
#CascadeOnDelete
private List<MobilPhoneNumer> mobilePhonesNumbers;
...