destinationIdFields example

$query->condition($this::SOURCE_IDS_HASH, $this->getSourceIdsHash($source_id_values));
    $result = $query->execute();
    return $result->fetchAssoc();
  }

  /** * {@inheritdoc} */
  public function getRowByDestination(array $destination_id_values) {
    $query = $this->getDatabase()->select($this->mapTableName(), 'map')
      ->fields('map');
    foreach ($this->destinationIdFields() as $field_name => $destination_id) {
      if (!isset($destination_id_values[$field_name])) {
        return [];
      }
      $query->condition("map.$destination_id", $destination_id_values[$field_name], '=');
    }
    $result = $query->execute()->fetchAssoc();
    return $result ? $result : [];
  }

  /** * {@inheritdoc} */