code: func (s *SQLStore) scheduleSubStoreFlush(ss *SQLSubStore) {
  	needSignal := false
  	f := s.ssFlusher
  	f.Lock()
  	f.stores[ss] = struct{}{}
  	if !f.signaled {
  		f.signaled = true
  		needSignal = true
  	}
  	f.Unlock()
  	if needSignal {
  		select {
  		case f.signalCh <- struct{}{}:
  		default:
  		}
  	}
  }
docs: // Add this store to the list of SubStore needing flushing
  // and signal the go-routine responsible for flushing if
  // need be.