private function finish()
    {
        if ($this->main_database !== null) {
            $this->main_database->disconnect();
        }

        $this->microtime_end = microtime(true);
        $this->microtime_elapsed = $this->microtime_end - $this->microtime_start;
        $this->traceLog("Execution time", sprintf("%.3f ms", $this->microtime_elapsed * 1000));
    }