ACP2E-1697: Catalog Rule Product indexer is slow

Author: dhorytskyi

lib/internal/Magento/Framework/Model/ResourceModel/Iterator.php

@@ -33,9 +33,7 @@ public function walk($query, array $callbacks, array $args = [], $connection = n
             foreach ($callbacks as $callback) {
                 $result = call_user_func($callback, $args);
                 if (!empty($result)) {
-                    foreach ((array)$result as $key => $value) {
-                        $args[$key] = $value;
-                    }
+                    $args = array_merge($args, (array)$result);
                 }
             }
             $args['idx']++;