Issue #3520750 by alexpott: Use a transaction PoDatabaseWriter to improve performance

   * {@inheritdoc}

   */

  public function writeItems(PoReaderInterface $reader, $count = -1) {

    // Processing multiple writes in a transaction is quicker than committing

    // each individual write.

    $transaction = \Drupal::database()->startTransaction();

    $forever = $count == -1;

    while (($count-- > 0 || $forever) && ($item = $reader->readItem())) {

      $this->writeItem($item);

    }

    // Commit the transaction.

    unset($transaction);

  }

  /**