diff --git a/maX.go b/maX.go
index a6cde8c..ee4dd4c 100644
--- a/maX.go
+++ b/maX.go
@@ -136,13 +136,12 @@ func (mxl *MaXList) RPush(sm *MaX) (Sample, error) {
 		mxl.List = append(mxl.List, sm)
 		return nil, nil
 	}
-	return nil, nil
 }
 
 // 冒泡排序
 func (mxl *MaXList) RecursiveBubbleS(length int, ctype string) error {
 	if length == 0 {
-		return nil
+		return errors.New("length is zero")
 	}
 	realLength := len(mxl.List)
 	//FIXME：在对这个List进行排序时，List中途长度变了，就会报错：
@@ -166,6 +165,6 @@ func (mxl *MaXList) RecursiveBubbleS(length int, ctype string) error {
 		}
 	}
 	length--
-	mxl.RecursiveBubbleS(length, ctype)
-	return nil
+	err := mxl.RecursiveBubbleS(length, ctype)
+	return err
 }
diff --git a/plate.go b/plate.go
index db146ad..178274b 100644
--- a/plate.go
+++ b/plate.go
@@ -113,19 +113,22 @@ func (pl *Plate) MakeCoaster(cr *Core, period string) error {
 	if err != nil {
 		return err
 	}
-	cdl.RecursiveBubbleS(len(cdl.List), "asc")
+	err = cdl.RecursiveBubbleS(len(cdl.List), "asc")
 	setName7 := "ma7|" + setName
 	setName30 := "ma30|" + setName
 	mxl7, err := cr.GetRangeMaXSortedSet(setName7, pl.Count, lastTime)
 	if err != nil {
 		return err
 	}
-	mxl7.RecursiveBubbleS(len(mxl7.List), "asc")
+	err = mxl7.RecursiveBubbleS(len(mxl7.List), "asc")
+	if err != nil {
+		return err
+	}
 	mxl30, err := cr.GetRangeMaXSortedSet(setName30, pl.Count, lastTime)
 	if err != nil {
 		return err
 	}
-	mxl30.RecursiveBubbleS(len(mxl30.List), "asc")
+	err = mxl30.RecursiveBubbleS(len(mxl30.List), "asc")
 	coaster := Coaster{
 		InstID:     pl.InstID,
 		Period:     period,