code: protected function generateDependencyData($cache)
      {
          /* @var $db Connection */
          $db = Instance::ensure($this->db, Connection::className());
          if ($this->sql === null) {
              throw new InvalidConfigException('DbDependency::sql must be set.');
          }
  
          if ($db->enableQueryCache) {
              // temporarily disable and re-enable query caching
              $db->enableQueryCache = false;
              $result = $db->createCommand($this->sql, $this->params)->queryOne();
              $db->enableQueryCache = true;
          } else {
              $result = $db->createCommand($this->sql, $this->params)->queryOne();
          }
  
          return $result;
      }
docs: Generates the data needed to determine if dependency has been changed.
  This method returns the value of the global state.
  @param CacheInterface $cache the cache component that is currently evaluating this dependency
  @return mixed the data needed to determine if dependency has been changed.
  @throws InvalidConfigException if [[db]] is not a valid application component ID