I have a weird database setup that I’d like to map with hibernate, with a table user and a table table post, with a many to many relationship between them, but the relationship is done via a a join table, which is referencing the primary key of user, but not the primary key of post, it’s referencing a non unique column of that table.

I managed to map it using @ManyToMany() with the code below, and it seems to work, but I’m wondering if referencing a non unique column is a good thing or if I shouldn’t because it can break on some edge cases.

user (
  id -- pkey
)

post (
  id -- pkey
  join_id -- non unique
)

user_posts (
  user_id -- references user.id
  post_join_id -- references post.join_id
)

In java :

public class User {
    @Id
    long id;
    
    @ManyToMany()
    @JoinTable(
        name = "user_posts",
        joinColumns = @JoinColumn(
            name = "user_id",
            referencedColumnName = "id"
        ),
        inverseJoinColumns = @JoinColumn(
            name = "post_join_id",
            referencedColumnName = "join_id"
        )
    )
    Set<Post> posts;
}

public class Post {
    @Id
    long id;
    
    long join_id;
}

Considering that multiple posts have the same join_id, is that the right way to do that mapping? I can’t find much info about doing such joins on non unique columns.

Thanks.