public function addDocumentInfo(PHPCrawlerDocumentInfo $DocInfo)
  {
    // If queue is full -> wait a little
    while ($this->getDocumentInfoCount() >= $this->queue_max_size)
    {
      sleep(0.5);
    }
    
    $this->createPreparedStatements();
    
    $ser = serialize($DocInfo);
    
    $this->PDO->exec("BEGIN EXCLUSIVE TRANSACTION");
    $this->prepared_insert_statement->bindParam(1, $ser, PDO::PARAM_LOB);
    $this->prepared_insert_statement->execute();
    $this->prepared_select_statement->closeCursor();
    $this->PDO->exec("COMMIT");
  }