Is it possible to use result of an SQL function as a field in Doctrine?

Question

Assume I have Product entities and Review entities attached to products. Is it possible to attach a fields to a Product entity based o

Answer 1

You can map a single column result to an entity field - look at native queries and ResultSetMapping to achieve this. As a simple example:

use Doctrine\ORM\Query\ResultSetMapping;

$sql = '
    SELECT p.*, COUNT(r.id)
    FROM products p
    LEFT JOIN reviews r ON p.id = r.product_id
';

$rsm = new ResultSetMapping;
$rsm->addEntityResult('AppBundle\Entity\Product', 'p');
$rsm->addFieldResult('p', 'COUNT(id)', 'reviewsCount');

$query   = $this->getEntityManager()->createNativeQuery($sql, $rsm);
$results = $query->getResult();

Then in your Product entity you would have a $reviewsCount field and the count would be mapped to that. Note that this will only work if you have a column defined in the Doctrine metadata, like so:

/**
 * @ORM\Column(type="integer")
 */
private $reviewsCount;

public function getReviewsCount()
{
    return $this->reviewsCount;
}

This is what is suggested by the Aggregate Fields Doctrine documentation. The problem is here is that you are essentially making Doctrine think you have another column in your database called reviews_count, which is what you don't want. So, this will still work without physically adding that column, but if you ever run a doctrine:schema:update it's going to add that column in for you. Unfortunately Doctrine does not really allow virtual properties, so another solution would be to write your own custom hydrator, or perhaps subscribe to the loadClassMetadata event and manually add the mapping yourself after your particular entity (or entities) load.

Note that if you do something like COUNT(r.id) AS reviewsCount then you can no longer use COUNT(id) in your addFieldResult() function, and must instead use the alias reviewsCount for that second parameter.

You can also use the ResultSetMappingBuilder as a start into using the result set mapping.

My actual suggestion is to do this manually instead of going through all of that extra stuff. Essentially create a normal query that returns both your entity and scalar results into an array, then set the scalar result to a corresponding, unmapped field on your entity, and return the entity.