Symfony/Doctrine relation COUNT in entity - symfony

Question

As the title states,
I would like to run 1 query to get results from a table with the count of their respective relationships.
Lets say I have a Person entity with a OneToMany relationship with a Friend entity
The Person entity might look something like the following:
class Person
{
/**
* #ORM\OneToMany(...)
*/
protected $friends;
public function __construct()
{
$this->friends = new ArrayCollection();
}
...
}
A classic SQL solution to what I want to achieve might look like the following:
SELECT p.*, COUNT(f.id) as friendsCount
FROM Persons p
LEFT JOIN Friends f
ON f.person_id = p.id
GROUP BY p.id
Now I am wondering if this could be done in DQL as well and storing the count value into the Person Entity
Lets say I expand the Person entity like: (Keep in mind this is just an idea)
class Person
{
/**
* #ORM\OneToMany(...)
*/
protected $friends;
protected $friendsCount;
public method __construct()
{
$this->friends = new ArrayCollection();
}
...
public function getFriendsCount()
{
return $this->friendsCount;
}
}
Now I am having trouble finding how I could populate the count value in the entity from DQL:
SELECT p, /* What comes here ? */
FROM AppBundle\Entity\Person p
LEFT JOIN p.friends f
GROUP BY p.id
PS: I do know I could just do:
$person->getFriends()->count();
And even mark it as extra lazy to get the count result.
I just though this count relationships example demonstrated well what I am trying to do.
(Which is populating the entity's non #ORM\Column properties from dql)
Is this possible with Doctrine ?
Is this breaking some solid principles ? (SRP ?)
Cookie for your thoughs ;)

Answer 1

You probably just want to select the count as you need it, as described above with $person->getFriends()->count();. However, you can select both an object and a count at the same time (see these Doctrine query examples), there is one very similar to what you are doing:
SELECT p, COUNT(p.friends)
FROM AppBundle\Entity\Person p
LEFT JOIN p.friends f
GROUP BY p.id
What should be returned back is an array of arrays with the object and count, like so:
[
[Person, int],
[Person, int],
...,
]
Your best bet would be to make that a Repository call on your PersonRepository, something like findPersonsWithFriendCount(), which would look like:
public function findPersonsWithFriendCount()
{
$persons = array();
$query = $this->_em->createQuery('
SELECT p, COUNT(p.friends)
FROM AppBundle\Entity\Person p
LEFT JOIN p.friends f
GROUP BY p.id
');
$results = $query->getResult();
foreach ($results as $result) {
$person = $result[0];
$person->setFriendsCount($result[1]);
$persons[] = $person;
}
return $persons;
}
Keep in mind you'd need to add a setFriendsCount() function on your Person object. You could also write a native SQL query and use result set mapping to automatically map your raw result's columns to your entity fields.