How to select discriminator column in doctrine 2 - php

Question

I need some help when select only discriminator column from doctrine 2 when run the DQL below
SELECT p.type FROM AppBundle\Entity\Product p
type is discriminator column in entity AppBundle\Entity\Product
#ORM\DiscriminatorColumn(name="type", type="smallint")`
#ORM\DiscriminatorMap({
"0" = "AppBundle\Entity\Product",
"1" = "AppBundle\Entity\Product\SingleIssue",
"2" = "AppBundle\Entity\Product\CountBasedIssue",
"3" = "AppBundle\Entity\Product\TimeBasedIssue"
})
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 Doctrine\ORM\Query\SqlWalker;
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 Doctrine\ORM\Internal\Hydration\ArrayHydrator;
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: YourNamespace\To\CustomHydrator
Final step
$query = $queryBuilder->getQuery();
$query->setHint(\Doctrine\ORM\Query::HINT_CUSTOM_OUTPUT_WALKER, 'YourNamespace\To\CustomSqlWalker');
$query->setHint(\YourNamespace\To\CustomSqlWalker::FORCE_GET_DISCRIMINATOR_COLUMN, array($rootAlias)); // this alias will be used in CustomSqlWalker class
$query->setHint(\YourNamespace\To\CustomSqlWalker::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 AppBundle\Entity\AbstractProduct product WHERE product INSTANCE OF AppBundle\Entity\Product");
$products = $query->getResult();
Hope this helps

Answer 2

I use this little "hack"
Define a common interface for your entities (optional but recommended)
Create a getType method in this interface
Create constant into Discriminator entity
Return the proper constant inside every discriminated entity
That way you can retrieve the discriminator "generic" entity (Product in your case) and call getType onto it.
Of course if you're interested into result filtering done directly by sql, this is not a solution at all and, I'm afraid, there isn't any solution available at the moment.
If you find one better that this, please share with us.

Answer 3

You should be able to do this with a scalar result with INSTANCE OF and a case, when, (else,) end clause:
SELECT
(case
when p INSTANCE OF AppBundle\Entity\Product then \'0\'
when p INSTANCE OF AppBundle\Entity\Product\SingleIssue then \'1\'
when p INSTANCE OF AppBundle\Entity\Product\CountBasedIssue then \'2\'
when p INSTANCE OF AppBundle\Entity\Product\TimeBasedIssue then \'3\'
else \'foobar\'
end) as type
FROM
AppBundle\Entity\Product p
Of course the disadvantage is you have to update the query every time you add a DiscriminatorMap entry.