class StatisticsLastCommentName

class StatisticsLastCommentName extends SortPluginBase {
  
  /**
   * The users table.
   */
  protected $user_table;
  
  /**
   * The user name field.
   */
  protected $user_field;
  public function query() {
    $this->ensureMyTable();
    $definition = [
      'table' => 'users_field_data',
      'field' => 'uid',
      'left_table' => 'comment_entity_statistics',
      'left_field' => 'last_comment_uid',
    ];
    $join = \Drupal::service('plugin.manager.views.join')->createInstance('standard', $definition);
    // @todo this might be safer if we had an ensure_relationship rather than guessing
    // the table alias. Though if we did that we'd be guessing the relationship name
    // so that doesn't matter that much.
    $this->user_table = $this->query
      ->ensureTable('ces_users', $this->relationship, $join);
    $this->user_field = $this->query
      ->addField($this->user_table, 'name');
    // Add the field.
    $this->query
      ->addOrderBy(NULL, "LOWER(COALESCE({$this->user_table}.name, {$this->tableAlias}.{$this->field}))", $this->options['order'], $this->tableAlias . '_' . $this->field);
  }

}