yii\mongodb\file\Collection::ensureFileIndexes PHP Method

    private function ensureFileIndexes()
    {
        $indexKey = ['filename' => 1, 'uploadDate' => 1];
        foreach ($this->listIndexes() as $index) {
            if ($index['key'] === $indexKey) {
                return;
            }
        }
        $this->createIndex($indexKey);
    }