Doctor DQL Manytomany查询以预取外部实体

Question

I have a User entity and Role entity. A user can have many roles and a role can have many users. The parts that matter (I think) are the following:

In User.php

/**
 * @ORM\ManyToMany(targetEntity="Role",inversedBy="users")
 * @ORM\JoinTable(name="user_role",
 *      joinColumns={@ORM\JoinColumn(name="userid", referencedColumnName="id")},
 *      inverseJoinColumns={@ORM\JoinColumn(name="roleid", referencedColumnName="id")}
 *      )
 */
protected $roles;
public function __construct(){
    $this->roles = new ArrayCollection();
}

In Role.php:

/**
 * @ORM\ManyToMany(targetEntity="User", mappedBy="roles")
 * @ORM\JoinTable(name="user_role",
 *      joinColumns={@ORM\JoinColumn(name="roleid", referencedColumnName="id")},
 *      inverseJoinColumns={@ORM\JoinColumn(name="userid", referencedColumnName="id")}
 *      )
 */
protected $users;
public function __construct(){
    $this->users = new ArrayCollection();
}

Trying the following query gives me a User that gets it's id and name field replaced with Role id and name

$result = $this->getEntityManager()->createQuery('SELECT 
    u.id, u.username, u.name, u.email, r.id, r.name
    FROM mytestBundle:User u
    LEFT JOIN u.roles r
    WHERE u.id = :id')
        ->setParameter('id', $id)
        ->getArrayResult();

The following gives me an error: Error: Cannot select entity through identification variables without choosing at least one root entity alias.

$result = $this->getEntityManager()->createQuery('SELECT 
    u.id, u.name, r
    //... rest is same

The following gives me the result as I expect but includes too many user fields. One user watching the profile of another user can't see the user's email, password, salt, ... but is allowed to see the user's roles:

$result = $this->getEntityManager()->createQuery('SELECT 
    u, r

So the question is: How do I select only certain user fields and have doctrine nest Roles in a user record without it throwing an error?

Answer 1

Posted too early, sorry.

This errors is quite common and many SO answers do not apply to my situation but this one does.

Using partial solved my problem:

$result = $this->getEntityManager()->createQuery('SELECT 
    partial u.{id, name}, r