Doctrine2 Query where Subquery would be needed - mysql

Question

Let me first introduce the Entities used in this example:
Order (_order in mysql)
$id (primary key, auto increment)
OrderStatus (order_status in mysql)
$id (primary key, auto increment)
$order (storing the order object it is related to, named order_id in mysql)
$statuscode (Storing the integer code)
$created_at (Storing the datetime of creation)
The relationship is Order n:1 OrderStatus. For every status change, I create a new OrderStatus with the new statuscode. So for one Order there can be many OrderStatus. The actual OrderStatus can be figured out by looking at the OrderStatus with the latest created_at.
I now want to get all objects which have the status 0 right now. In SQL, my query would look like this:
SELECT o.id,os.statuscode,os.created_at
FROM `_order` o
LEFT JOIN `order_status` os ON o.id = os.order_id
WHERE os.created_at = (SELECT MAX(created_at)
FROM order_status
WHERE order_id = os.order_id);
Can I do such a query in DQL or do I have to work with objects? If so, would I need to read all OrderStatus objects and manually figure out which is the most current one or can I somehow preselect?

Answer 1

I figured out a way which is not quite what I was searching for, but it doesn't require any changes in my application, so it's ok as long as I don't find a better solution.
What I'll do is I'll store the actual status directly within the Order. Through LifecycleCallbacks I'll update the order as soon as a OrderStatus related to it is created.
So my Order-Object looks like this:
/**
* #ORM\Entity
* #ORM\Table(name="_order")
*/
class Order{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
//..
/**
* #ORM\Column(type="smallint", nullable=false)
*/
protected $status = -1;
// Getter and Setter!
}
My Order-Status will look like this:
/**
* #ORM\Entity
* #ORM\Table(name="order_status")
* #ORM\HasLifecycleCallbacks
*/
class OrderStatus{
/**
* #ORM\Id
* #ORM\Column(type="integer")
* #ORM\GeneratedValue(strategy="AUTO")
*/
protected $id;
/**
* #ORM\ManyToOne(targetEntity="Order", inversedBy="order_status", cascade={"persist"})
* #ORM\JoinColumn(name="order_id", referencedColumnName="id", nullable=false)
*/
protected $order;
/**
* #ORM\Column(type="smallint", nullable=false)
*/
protected $statuscode;
// ..
/**
* #ORM\prePersist
*/
public function prePersist(){
$this->order->setStatus($this->statuscode);
}
// Getter and Setter!
}
Mind the , cascade={"persist"} within the OrderStatus so the Order will also be persisted when the OrderStatus is persisted, otherwise the status will be set, but not stored!
On the plus side of this solution is that I now get the OrderStatus by calling $order->getStatus() instead of having to query the database for the status and that I'm able to do $repository->findByStatus(0). On the other hand, the moment the status field gets changed due to some error, the data will be inconsistent.
As said, if you got a solution where I don't need an extra field to store the status, post it! I'm very interested in a better solution!