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;
    }

}