class TermNode

class TermNode extends DrupalSqlBase {

  /**
   * The join options between the node and the term node table.
   */
  const JOIN = '[tn].[vid] = [n].[vid]';

  /**
   * {@inheritdoc}
   */
  public function query() {
    $query = $this
      ->select('term_node', 'tn')
      ->distinct()
      ->fields('tn', [
      'nid',
      'vid',
    ])
      ->fields('n', [
      'type',
    ]);

    // Because this is an inner join it enforces the current revision.
    $query
      ->innerJoin('term_data', 'td', '[td].[tid] = [tn].[tid] AND [td].[vid] = :vid', [
      ':vid' => $this->configuration['vid'],
    ]);
    $query
      ->innerJoin('node', 'n', static::JOIN);
    return $query;
  }

  /**
   * {@inheritdoc}
   */
  public function fields() {
    return [
      'nid' => $this
        ->t('The node revision ID.'),
      'vid' => $this
        ->t('The node revision ID.'),
      'tid' => $this
        ->t('The term ID.'),
    ];
  }

  /**
   * {@inheritdoc}
   */
  public function prepareRow(Row $row) {

    // Select the terms belonging to the revision selected.
    $query = $this
      ->select('term_node', 'tn')
      ->fields('tn', [
      'tid',
    ])
      ->condition('n.nid', $row
      ->getSourceProperty('nid'));
    $query
      ->join('node', 'n', static::JOIN);
    $query
      ->innerJoin('term_data', 'td', '[td].[tid] = [tn].[tid] AND [td].[vid] = :vid', [
      ':vid' => $this->configuration['vid'],
    ]);
    $row
      ->setSourceProperty('tid', $query
      ->execute()
      ->fetchCol());
    return parent::prepareRow($row);
  }

  /**
   * {@inheritdoc}
   */
  public function getIds() {
    $ids['vid']['type'] = 'integer';
    $ids['vid']['alias'] = 'tn';
    return $ids;
  }

}