code: func (h *Handle) Clear() {
  	h.mu.Lock()
  	h.StatsCache.Store(StatsCache{})
  	h.mu.lastVersion = 0
  	for len(h.ddlEventCh) > 0 {
  		<-h.ddlEventCh
  	}
  	h.feedback = h.feedback[:0]
  	h.mu.ctx.GetSessionVars().InitChunkSize = 1
  	h.mu.ctx.GetSessionVars().MaxChunkSize = 32
  	h.listHead = &SessionStatsCollector{mapper: make(tableDeltaMap), rateMap: make(errorRateDeltaMap)}
  	h.globalMap = make(tableDeltaMap)
  	h.mu.rateMap = make(errorRateDeltaMap)
  	h.mu.Unlock()
  }
docs: // Clear the StatsCache, only for test.