Doctrine 2: Load entity and childs count

I have these two entities:

Message entity

class Message
{
    /**
    * @ManyToOne(targetEntity="User")
    * @JoinColumn(name="author", referencedColumnName="id_user")
    */
    protected $author;

User entity

class User
{
    /**
     * @Id
     * @Column(type="integer", nullable=false, name="id_user")
     * @GeneratedValue(strategy="AUTO")
     */
    protected $id;

    /**
     * @Column(type="string", nullable=false)
     */
    protected $name;

I need to get the total of messages of user and its data in order to echo something like this:

echo $user->getName() . " have {$user->totalOfMessage()}";

I now that I can make a relation in User entity to get a message collection. But I don’t know if it necessary only to get the size.

Answer

Well, I found the answer. At least one good option.

As of Doctrine 2.1 you can mark associations as extra lazy. This means that calling $user->getMessages()->count() won’t load the messages, it will just issue a COUNT query to the database.

You can read about extra lazy collections here: https://www.doctrine-project.org/projects/doctrine-orm/en/2.7/tutorials/extra-lazy-associations.html