code: public function init()
      {
          parent::init();
          if ($this->defaultSchema === null) {
              $username = $this->db->username;
              if (empty($username)) {
                  $username = isset($this->db->masters[0]['username']) ? $this->db->masters[0]['username'] : '';
              }
              $this->defaultSchema = strtoupper($username);
          }
      }
docs: {@inheritdoc}