update

Signed-off-by: Weizhen Wang <wangweizhen@pingcap.com>

pkg/statistics/histogram.go

@@ -1545,7 +1545,7 @@ func MergePartitionHist2GlobalHist(sc *stmtctx.StatementContext, hists []*Histog
 
 	// Calc the bucket lower.
 	if minValue == nil || len(globalBuckets) == 0 { // both hists and popedTopN are empty, returns an empty hist in this case
-		if len(globalBuckets) == 0 {
+		if len(hists) == 0 {
 			logutil.BgLogger().Info("debug info for MergePartitionHist2GlobalHist")
 		}
 		return NewHistogram(hists[0].ID, 0, totNull, hists[0].LastUpdateVersion, hists[0].Tp, len(globalBuckets), totColSize), nil