Fixing memory leak in ResultSet

As a side effect of this fix, the $_query propery of ResultSet
was removed. The query will not appear anymore as part of the
__debugInfo() for a ResultSet anymore as a consequence of this.

src/ORM/ResultSet.php

@@ -38,6 +38,7 @@ class ResultSet implements ResultSetInterface
      * Original query from where results were generated
      *
      * @var Query
+     * @deprecated 3.1.6 Due to a memory leak, this property cannot be used anymore
      */
     protected $_query;
 
@@ -169,16 +170,15 @@ class ResultSet implements ResultSetInterface
     public function __construct($query, $statement)
     {
         $repository = $query->repository();
-        $this->_query = $query;
         $this->_statement = $statement;
-        $this->_driver = $this->_query->connection()->driver();
-        $this->_defaultTable = $this->_query->repository();
-        $this->_calculateAssociationMap();
-        $this->_hydrate = $this->_query->hydrate();
+        $this->_driver = $query->connection()->driver();
+        $this->_defaultTable = $query->repository();
+        $this->_calculateAssociationMap($query);
+        $this->_hydrate = $query->hydrate();
         $this->_entityClass = $repository->entityClass();
         $this->_useBuffering = $query->bufferResults();
         $this->_defaultAlias = $this->_defaultTable->alias();
-        $this->_calculateColumnMap();
+        $this->_calculateColumnMap($query);
         $this->_calculateTypeMap();
 
         if ($this->_useBuffering) {
@@ -347,11 +347,12 @@ class ResultSet implements ResultSetInterface
      * Calculates the list of associations that should get eager loaded
      * when fetching each record
      *
+     * @param \Cake\ORM\Query $query The query from where to derive the associations
      * @return void
      */
-    protected function _calculateAssociationMap()
+    protected function _calculateAssociationMap($query)
     {
-        $map = $this->_query->eagerLoader()->associationsMap($this->_defaultTable);
+        $map = $query->eagerLoader()->associationsMap($this->_defaultTable);
         $this->_matchingMap = (new Collection($map))
             ->match(['matching' => true])
             ->indexBy('alias')
@@ -367,12 +368,13 @@ class ResultSet implements ResultSetInterface
      * Creates a map of row keys out of the query select clause that can be
      * used to hydrate nested result sets more quickly.
      *
+     * @param \Cake\ORM\Query $query The query from where to derive the column map
      * @return void
      */
-    protected function _calculateColumnMap()
+    protected function _calculateColumnMap($query)
     {
         $map = [];
-        foreach ($this->_query->clause('select') as $key => $field) {
+        foreach ($query->clause('select') as $key => $field) {
             $key = trim($key, '"`[]');
             if (strpos($key, '__') > 0) {
                 $parts = explode('__', $key, 2);
@@ -622,7 +624,6 @@ class ResultSet implements ResultSetInterface
     public function __debugInfo()
     {
         return [
-            'query' => $this->_query,
             'items' => $this->toArray(),
         ];
     }

tests/TestCase/ORM/QueryRegressionTest.php

@@ -1181,4 +1181,29 @@ class QueryRegressionTest extends TestCase
         $result = $query->all();
         $this->assertCount(3, $result);
     }
+
+    /**
+     * Tests that decorating the results does not result in a memory leak
+     *
+     * @return void
+     */
+    public function testFormatResultsMemory()
+    {
+        $table = TableRegistry::get('Articles');
+        $table->belongsTo('Authors');
+        $table->belongsToMany('Tags');
+        gc_collect_cycles();
+        $memory = memory_get_usage() / 1024 / 1024;
+        foreach (range(1, 3) as $time) {
+                $table->find()
+                ->contain(['Authors', 'Tags'])
+                ->formatResults(function ($results) {
+                    return $results;
+                })
+                ->all();
+        }
+        gc_collect_cycles();
+        $endMemory = memory_get_usage() / 1024 / 1024;
+        $this->assertWithinRange($endMemory, $memory, 1.25, 'Memory leak in ResultSet');
+    }
 }

tests/TestCase/ORM/ResultSetTest.php

@@ -260,7 +260,6 @@ class ResultSetTest extends TestCase
         $query = $this->table->find('all');
         $results = $query->all();
         $expected = [
-            'query' => $query,
             'items' => $results->toArray()
         ];
         $this->assertSame($expected, $results->__debugInfo());