code: func (t *copTask) finishIndexPlan() {
  	if !t.indexPlanFinished {
  		t.cst += t.count() * netWorkFactor
  		t.indexPlanFinished = true
  		if t.tablePlan != nil {
  			t.tablePlan.(*PhysicalTableScan).stats = t.indexPlan.statsInfo()
  			t.cst += t.count() * scanFactor
  		}
  	}
  }
docs: // finishIndexPlan means we no longer add plan to index plan, and compute the network cost for it.