class Term

class Term extends DrupalSqlBase {
  
  /**
   * {@inheritdoc}
   */
  public function query() {
    $query = $this->select('term_data', 'td')
      ->fields('td')
      ->distinct()
      ->orderBy('td.tid');
    if (isset($this->configuration['bundle'])) {
      $query->condition('td.vid', (array) $this->configuration['bundle'], 'IN');
    }
    return $query;
  }
  
  /**
   * {@inheritdoc}
   */
  public function fields() {
    $fields = [
      'tid' => $this->t('The term ID.'),
      'vid' => $this->t('Existing term VID'),
      'name' => $this->t('The name of the term.'),
      'description' => $this->t('The term description.'),
      'weight' => $this->t('Weight'),
      'parent' => $this->t("The Drupal term IDs of the term's parents."),
    ];
    if (isset($this->configuration['translations'])) {
      $fields['language'] = $this->t('The term language.');
      $fields['trid'] = $this->t('Translation ID.');
    }
    return $fields;
  }
  
  /**
   * {@inheritdoc}
   */
  public function prepareRow(Row $row) {
    // Find parents for this row.
    $parents = $this->select('term_hierarchy', 'th')
      ->fields('th', [
      'parent',
      'tid',
    ])
      ->condition('tid', $row->getSourceProperty('tid'))
      ->execute()
      ->fetchCol();
    $row->setSourceProperty('parent', $parents);
    return parent::prepareRow($row);
  }
  
  /**
   * {@inheritdoc}
   */
  public function getIds() {
    $ids['tid']['type'] = 'integer';
    return $ids;
  }

}