[DDC-1783] Fix memory leak in ObjectHydrator when using AbstractQuery#iterate() and EntityManager#clear()

lib/Doctrine/ORM/Internal/Hydration/AbstractHydrator.php

@@ -23,6 +23,7 @@ use PDO,
     Doctrine\DBAL\Connection,
     Doctrine\DBAL\Types\Type,
     Doctrine\ORM\EntityManager,
+    Doctrine\ORM\Events,
     Doctrine\ORM\Mapping\ClassMetadata;
 
 /**
@@ -83,6 +84,9 @@ abstract class AbstractHydrator
         $this->_rsm   = $resultSetMapping;
         $this->_hints = $hints;
 
+        $evm = $this->_em->getEventManager();
+        $evm->addEventListener(array(Events::onClear), $this);
+
         $this->prepare();
 
         return new IterableResult($this);
@@ -375,4 +379,12 @@ abstract class AbstractHydrator
 
         $this->_em->getUnitOfWork()->registerManaged($entity, $id, $data);
     }
+
+    /**
+     * When executed in a hydrate() loop we have to clear internal state to
+     * decrease memory consumption.
+     */
+    public function onClear($eventArgs)
+    {
+    }
 }

lib/Doctrine/ORM/Internal/Hydration/ObjectHydrator.php

@@ -54,7 +54,6 @@ class ObjectHydrator extends AbstractHydrator
     private $_rootAliases = array();
     private $_initializedCollections = array();
     private $_existingCollections = array();
-    //private $_createdEntities;
 
 
     /** @override */
@@ -527,4 +526,20 @@ class ObjectHydrator extends AbstractHydrator
             }
         }
     }
+
+    /**
+     * When executed in a hydrate() loop we may have to clear internal state to
+     * decrease memory consumption.
+     */
+    public function onClear($eventArgs)
+    {
+        parent::onClear($eventArgs);
+
+        $aliases              = array_keys($this->_identifierMap);
+        $this->_identifierMap = array();
+
+        foreach ($aliases as $alias) {
+            $this->_identifierMap[$alias] = array();
+        }
+    }
 }

tests/Doctrine/Tests/ORM/Functional/QueryTest.php

@@ -227,6 +227,42 @@ class QueryTest extends \Doctrine\Tests\OrmFunctionalTestCase
         $this->_em->clear();
     }
 
+    public function testIterateResultClearEveryCycle()
+    {
+        $article1 = new CmsArticle;
+        $article1->topic = "Doctrine 2";
+        $article1->text = "This is an introduction to Doctrine 2.";
+
+        $article2 = new CmsArticle;
+        $article2->topic = "Symfony 2";
+        $article2->text = "This is an introduction to Symfony 2.";
+
+        $this->_em->persist($article1);
+        $this->_em->persist($article2);
+
+        $this->_em->flush();
+        $this->_em->clear();
+
+        $query    = $this->_em->createQuery("select a from Doctrine\Tests\Models\CMS\CmsArticle a");
+        $articles = $query->iterate();
+
+        $iteratedCount = 0;
+        $topics = array();
+        foreach($articles AS $row) {
+            $article  = $row[0];
+            $topics[] = $article->topic;
+
+            $this->_em->clear();
+
+            $iteratedCount++;
+        }
+
+        $this->assertEquals(array("Doctrine 2", "Symfony 2"), $topics);
+        $this->assertEquals(2, $iteratedCount);
+
+        $this->_em->flush();
+    }
+
     /**
      * @expectedException \Doctrine\ORM\Query\QueryException
      */