getIdField example

// Optimize performance in case we have an object loader and         // a single-field identifier         if ($idReader && $this->objectLoader) {
            $objects = [];
            $objectsById = [];

            // Maintain order and indices from the given $values             // An alternative approach to the following loop is to add the             // "INDEX BY" clause to the Doctrine query in the loader,             // but I'm not sure whether that's doable in a generic fashion.             foreach ($this->objectLoader->getEntitiesByIds($idReader->getIdField(), $values) as $object) {
                $objectsById[$idReader->getIdValue($object)] = $object;
            }

            foreach ($values as $i => $id) {
                if (isset($objectsById[$id])) {
                    $objects[$i] = $objectsById[$id];
                }
            }

            return $objects;
        }