Doctrine2 - How can I order by a discriminator column?

Question

How should I go about ordering by a discriminator column in a doctrine repository query?

I have a pretty straight forward setup, I have different types of payment details, it can either be Credit Card (CC) or Debit Order (DO).

So I've implemented a single table inheritance mapping strategy to achieve this, but the problem now comes in when I try to order by the discriminator column, since the discriminator column isn't present in the base class.

The repository function:

public function getPaymentDetails (ClientContactInterface $clientContact)
{
    $dql = 'SELECT pd
            from
            AccountingBundle:PaymentDetail pd
            JOIN ClientProductBundle:ClientProduct cp
            WITH cp.payment_detail_id = pd.id
            WHERE
            cp.payment_detail_id = pd.id
            and cp.client_contact_id = :client_contact_id
            GROUP BY pd.id
            ORDER BY pd.method_type'; // Since pd.method_type is the discriminator column, I cannot order by it. And I need to be able to.

    $em = $this->getEntityManager();
    $query = $em->createQuery($dql)->setParameter('client_contact_id', $clientContact->getId());
    return $query->getResult();
}

Base PaymentDetail entity:

/**
 * @ORM\Entity(repositoryClass="AccountingBundle\Repository\PaymentDetailRepository")
 * @ORM\InheritanceType("SINGLE_TABLE")
 * @ORM\Table(name="PaymentDetails")
 * @ORM\DiscriminatorColumn(name="PaymentMethodType", type="string")
 * @ORM\DiscriminatorMap({ "DO" = "DOPaymentDetail", "CC" = "CCPaymentDetail"})
 */

class PaymentDetail implements PaymentDetailInterface
{

    /**
     * @var integer $id
     *
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    protected  $id;

    /* etc... */
}

Debit Order PaymentDetail entity:

/**
 * AccountingBundle\Entity\DOPaymentDetail
 *
 * @ORM\Table(name="PaymentDetails")
 * @ORM\Entity
 */
class DOPaymentDetail extends PaymentDetail implements DOPaymentDetailInterface
{

    /**
     * @var string $account_holder
     *
     * @ORM\Column(name="DOAccountHolder", type="string", length=255)
     */
    protected $account_holder;

    /* etc... */
}

Credit Card PaymentDetail entity:

/**
 * AccountingBundle\Entity\CCPaymentDetail
 *
 * @ORM\Table(name="PaymentDetails")
 * @ORM\Entity
 */
class CCPaymentDetail extends PaymentDetail implements CCPaymentDetailInterface
{

    /**
     *
     * @var string $card_holder
     *
     * @ORM\Column(name="CCCardHolder", type="string", length=255)
     */
    protected $card_holder;

    /* etc... */
}

When I try that, I get this error,

Error: Class AccountingBundle\Entity\PaymentDetail has no field or association named method_type") 

Answer 1

Even though TYPE is not implemented yet into the core of doctrine it's still possible to implement it as a custom user function.

Someone already did an amazing job and implemented it for us. Just in case the resource will be removed in the future, here is a slightly adjusted version for php7+:

<?php
use Doctrine\ORM\Mapping\ClassMetadataInfo;
use Doctrine\ORM\Query\AST\Functions\FunctionNode;
use Doctrine\ORM\Query\Lexer;
use Doctrine\ORM\Query\Parser;
use Doctrine\ORM\Query\QueryException;
use Doctrine\ORM\Query\SqlWalker;

class TypeFunction extends FunctionNode
{
    /**
     * @var string
     */
    public $dqlAlias;

    public function getSql(SqlWalker $sqlWalker): string
    {
        /** @var ClassMetadataInfo $class */
        $class = $sqlWalker->getQueryComponent($this->dqlAlias)['metadata'];
        $tableAlias = $sqlWalker->getSQLTableAlias($class->getTableName(), $this->dqlAlias);

        if (!isset($class->discriminatorColumn['name'])) {
            $message = 'TYPE() only supports entities with a discriminator column.';
            throw QueryException::semanticalError($message);
        }

        return $tableAlias . '.' . $class->discriminatorColumn['name'];
    }

    public function parse(Parser $parser)
    {
        $parser->match(Lexer::T_IDENTIFIER);
        $parser->match(Lexer::T_OPEN_PARENTHESIS);
        $this->dqlAlias = $parser->IdentificationVariable();
        $parser->match(Lexer::T_CLOSE_PARENTHESIS);
    }
}

Now you can order by the discriminator column by doing something like:

SELECT e, TYPE(e) AS HIDDEN my_type FROM Entity e ORDER BY my_type DESC;

Answer 2

It seems like the simplest solution (so far) is to add another field to the base class and copy the discriminator column value.

The aforementioned TYPE(q) works only in WHERE clause.