/**
 * Implements hook_node_update_index().
 */
function {{ machine_name }}_node_update_index(\Drupal\node\NodeInterface $node) {
  $text = '';
  $ratings = \Drupal::database()->query('SELECT title, description FROM {my_ratings} WHERE nid = :nid', [':nid' => $node->id()]);
  foreach ($ratings as $rating) {
    $text .= '<h2>' . Html::escape($rating->title) . '</h2>' . Xss::filter($rating->description);
  }
  return $text;
}