Ebean loads @OneToMany associations using OUTER JOIN

[davidonlaptop]

A similar issue was documented in the old bug tracking system (http://www.avaje.org/bugdetail-410.html), and discussed in the google group (https://groups.google.com/forum/#!topic/ebean/V6foc1K38Lk).

Excerpt from the discussion:

I have noticed that Ebean always load the associations using OUTER JOINS. I've tried with @OnetoOne, @onetomany, using a FetchConfig, or FetchType.LAZY, and still it always use an OUTER JOIN.

For example, I have a User model which has many books (object and db code at the end). If I load the user like this:

User user = User.find.fetch("books", new FetchConfig().query() ).where("id = 2").findUnique();

The first query loads the user:

select t0.id c0, t0.first_name c1, t0.last_name c2 
from users t0 
where t0.id = 2

The second query uses an outer join :

select t0.id c0
        , t1.id c1, t1.name c2, t1.user_id c3 
from users t0
left outer join books t1 on t1.user_id = t0.id
where t0.id = 2   
order by t0.id

However, I would expect the second query to be something like :

select t1.id c1, t1.name c2, t1.user_id c3 
from books t1
where t1.user_id = 2

Question 1. The user_id is already known by the first query, so why the join is required?
Question 2. Is there some way around this?

Code for models and SQL :

@Entity
@Table(name="users")
public class User
{
    @Id
    public int id;
    public String firstName;
    public String lastName;

    @OneToMany(mappedBy = "user")
    public List<Book> books;

    public static Finder<Integer,User> find = new Finder<Integer,User>( Integer.class, User.class );
}

@Entity
@Table(name="books")
public class Book
{
    @Id
    public int id;
    public String name;

    @ManyToOne
    public User user;

    public static Finder<Integer,Book> find = new Finder<Integer,Book>( Integer.class, Book.class );
}

And the SQL code is :
CREATE TABLE `users` (
  `id` int(11) NOT NULL,
  `first_name` varchar(45) DEFAULT NULL,
  `last_name` varchar(45) DEFAULT NULL,
  PRIMARY KEY (`id`)
);
INSERT INTO users VALUES(1,"Joe","Bloh");
INSERT INTO users VALUES(2,"Maria","Luis");
CREATE  TABLE `books` (
  `id` INT NOT NULL ,
  `user_id` INT NOT NULL ,
  `name` VARCHAR(45) NULL ,
  PRIMARY KEY (`id`)
);
INSERT INTO books VALUES(1,1,"Joe's first book");
INSERT INTO books VALUES(2,1,"Joe's second book");
INSERT INTO books VALUES(3,2,"Maria's first book");
INSERT INTO books VALUES(4,2,"Maria's second book");

[rbygrave]

This issue was fixed in version 3.3.2.