php - How to select discriminator column in doctrine 2

Question

I need some help when select only discriminator column from doctrine 2 when run the DQL below

SELECT p.type FROM AppBundleEntityProduct p

type is discriminator column in entity AppBundleEntityProduct

@ORMDiscriminatorColumn(name="type", type="smallint")`

@ORMDiscriminatorMap({
    "0" = "AppBundleEntityProduct",
    "1" = "AppBundleEntityProductSingleIssue",
    "2" = "AppBundleEntityProductCountBasedIssue",
    "3" = "AppBundleEntityProductTimeBasedIssue"
})

I know that type is not a real property in entity, but is there anyway for me to do that?

Thanks in advance!

Updated

After 2 days for reading Doctrine codes, I decided to override SqlWalker and create new Hydrator by the snippets below

Override SqlWalker

<?php

namespace ...;

use DoctrineORMQuerySqlWalker;

class CustomSqlWalker extends SqlWalker
{
    const FORCE_GET_DISCRIMINATOR_COLUMN = 'forceGetDiscriminatorColumn';
    const DISCRIMINATOR_CLASS_MAP = 'discriminatorClassMap';

    /**
     * {@inheritdoc}
     */
    public function walkSelectClause($selectClause)
    {
        $sql = parent::walkSelectClause($selectClause);
        $forceGetDiscriminatorColumn = $this->getQuery()->getHint(self::FORCE_GET_DISCRIMINATOR_COLUMN);
        if (empty($forceGetDiscriminatorColumn)) {
            return $sql;
        }

        foreach ($this->getQueryComponents() as $key => $queryComponent) {
            if (!in_array($key, $forceGetDiscriminatorColumn)) {
                continue;
            }

            $metadata = $queryComponent['metadata'];
            $discriminatorColumn = $metadata->discriminatorColumn['name'];
            $tableName = $metadata->table['name'];
            $tableAlias = $this->getSQLTableAlias($tableName, $key);
            $discriminatorColumnAlias = $this->getSQLColumnAlias($discriminatorColumn);
            $sql .= ", $tableAlias.$discriminatorColumn AS $discriminatorColumnAlias";
        }

        return $sql;
    }
}

Custom Hydrator

<?php

namespace ...;

use DoctrineORMInternalHydrationArrayHydrator;
use PDO;

class CustomHydrator extends ArrayHydrator
{
    /**
     * {@inheritdoc}
     */
    protected function hydrateAllData()
    {
        $result = array();

        $rootClassName = null;
        if (isset($this->_hints['forceGetDiscriminatorColumn']) &&
            isset($this->_hints['discriminatorClassMap'])) {
            $rootClassName = $this->_hints['discriminatorClassMap'];
        }

        while ($data = $this->_stmt->fetch(PDO::FETCH_ASSOC)) {
            foreach ($data as $key => $value) {
                if ($this->hydrateColumnInfo($key) != null ||
                    empty($rootClassName)) {
                    continue;
                }

                $metadata = $this->getClassMetadata($rootClassName);
                $discriminatorColumn = $metadata->discriminatorColumn;
                $fieldName = $discriminatorColumn['fieldName'];
                $type = $discriminatorColumn['type'];
                $this->_rsm->addScalarResult(
                    $key, $fieldName, $type
                );
            }
            $this->hydrateRowData($data, $result);
        }

        return $result;
    }
}

Configure custom hydrator

orm:
    ...
    hydrators:
        CustomHydrator: YourNamespaceToCustomHydrator

Final step

$query = $queryBuilder->getQuery();
$query->setHint(DoctrineORMQuery::HINT_CUSTOM_OUTPUT_WALKER, 'YourNamespaceToCustomSqlWalker');
$query->setHint(YourNamespaceToCustomSqlWalker::FORCE_GET_DISCRIMINATOR_COLUMN, array($rootAlias)); // this alias will be used in CustomSqlWalker class
$query->setHint(YourNamespaceToCustomSqlWalker::DISCRIMINATOR_CLASS_MAP, $this->getClassName()); // this full-qualify class name will be used in CustomHydrator class

$products = $query->getResult('CustomHydrator');

TL;DR

I know this is a very complicated solution (may be just for my scenario), so I hope someone could give me another simple way to fix that, thanks so much!

Answer 1

There is no direct access to the discriminator column.

It may happen that the entities of a special type should be queried. Because there is no direct access to the discriminator column, Doctrine provides the INSTANCE OF construct.

You can query for the type of your entity using the INSTANCE OF DQL as described in the docs. As example:

$query = $em->createQuery("SELECT product FROM AppBundleEntityAbstractProduct product WHERE product  INSTANCE OF AppBundleEntityProduct");
$products = $query->getResult();

Hope this helps