yii\mongodb\Query::distinct PHP Method

    public function distinct($q, $db = null)
    {
        $collection = $this->getCollection($db);
        if ($this->where !== null) {
            $condition = $this->where;
        } else {
            $condition = [];
        }
        $result = $collection->distinct($q, $condition);
        if ($result === false) {
            return [];
        } else {
            return $result;
        }
    }