Views handler to count the number of rows in a multigroup

I wanted to create a handler to list the number of rows in a multigroup. This is a working implementation ... but the way I've counted the number of rows in the group is pretty shameful. I couldn't find an API function or see any value in the database which looked like it would give me the information, so I resorted to counting the rows of the first required field in that multigroup.

Here be dragons:

/**
 * Implementation of hook_views_handlers().
 */
function content_multigroup_views_handlers() {
  return array(
    'info' => array(
      'path' => drupal_get_path('module', 'content_multigroup'),
    ),
    'handlers' => array(
      'content_multigroup_handler_field_multigroup_count' => array(
        'parent' => 'views_handler_field_custom',
      ),
    ),
  );
}

/**
 * Implementation of hook_views_data().
 */
function content_multigroup_views_data_alter(&$data) {
  // Scan all field groups in the system.
  foreach (fieldgroup_groups() as $type_name => $groups) {
    $type_label = node_get_types('name', $type_name);

    foreach ($groups as $group_name => $group) {
      // Let's focus on multigroups that really accept multiple values.
      if ($group['group_type'] == 'multigroup' && !empty($group['settings']['multigroup']['multiple'])) {
        $db_field = 'multigroup_count_'. $type_name .'_'. $group_name;

        $data['node'][$db_field] = array(
          'group' => t('Content'),
          'title' => t('Multigroup row count @t (@g)', array('@t' => $type_name, '@g' => $group_name)),
          'help' => t('Count the number of rows in a multigroup'),
          'real field' => NULL,
          'field' => array(
            'handler' => 'content_multigroup_handler_field_multigroup_count',
            'click sortable' => TRUE,
            'group_name' => $group_name,
          ),
        );
      }
    }
  }
}

/**
 * Views handler
 *
 * Count the number of rows in a multigroup
 */
class content_multigroup_handler_field_multigroup_count extends views_handler_field_custom {
  function render($values) {    
    // Field a field that exists in this group
    $res = db_query('SELECT cgf.field_name
      FROM content_group_fields cgf
      LEFT JOIN content_node_field cnf
      ON cgf.field_name = cnf.field_name
      WHERE type_name="%s"
        AND group_name="%s"
        AND cnf.required = 1',
        $values->node_type,
        $this->definition['group_name']);
    $field_name = db_result($res);

    // Count the number of rows for this vid and nid
    $res = db_query('SELECT COUNT(nid)
      FROM {content_'.$field_name.'}
      WHERE vid=%d and nid=%d',
        $values->node_vid,
        $values->nid);
    $count = db_result($res);

    return $count;
  }
}