protected function sendLongData(mysqli_stmt $statement, int $paramNr, ?string $data): void
  {
    if ($data!==null)
    {
      $n = strlen($data);
      $p = 0;
      while ($p<$n)
      {
        $b = $statement->send_long_data($paramNr, substr($data, $p, $this->chunkSize));
        if (!$b) $this->mySqlError('mysqli_stmt::send_long_data');
        $p += $this->chunkSize;
      }
    }
  }