Question

I have an entity that has a ManyToMany relationship with itself:

@Entity
public class User {

    @Id
    private Long id;

    @ManyToMany
    private List<User> friends;
}

How can I delete a user without deleting all of his friends? I cannot use cascading deletes obviously. If I try to delete the user without cascading I get a this error: “Cannot delete or update a parent row: a foreign key constraint fails”

Answer 1

Normally with ManyToMany we will map data in different tables, and the delete won’t create much of a problem. I feel your case is different an you are having a self relationship. I think you need to use some other ways to perform this action.

How can I delete a user without deleting all of his friends? The below option is one of them.

Considering your special mapping, List<User> in User, you should be only updating the mapping table references, and not deleting anything from the User table. Because they may have some other User as friends and that can create problems.