fix error

Signed-off-by: husharp <jinhao.hu@pingcap.com>

tikv/kv.go

@@ -585,12 +585,10 @@ func (s *KVStore) updateSafeTS(ctx context.Context) {
 	wg := &sync.WaitGroup{}
 	wg.Add(len(stores))
 	// Try to get the minimum resolved timestamp of the store from PD.
-	var (
-		storeIDs []string
-		err      error
-	)
-	for _, store := range stores {
-		storeIDs = append(storeIDs, strconv.FormatUint(store.StoreID(), 10))
+	var err error
+	storeIDs := make([]string, len(stores))
+	for i, store := range stores {
+		storeIDs[i] = strconv.FormatUint(store.StoreID(), 10)
 	}
 	storeMinResolvedTSs := make(map[uint64]uint64)
 	if s.pdHttpClient != nil {

util/pd.go

@@ -96,13 +96,16 @@ func (p *PDHTTPClient) GetMinResolvedTSByStoresIDs(ctx context.Context, storeIDs
 			logutil.BgLogger().Debug("failed to marshal store ids", zap.String("addr", addr), zap.Error(err))
 			return nil, errors.Trace(err)
 		}
-		v, e := pdRequest(ctx, addr, minResolvedTSPrefix, p.cli, http.MethodGet, bytes.NewBuffer(data))
-		if e != nil {
-			logutil.BgLogger().Debug("failed to get min resolved ts", zap.String("addr", addr), zap.Error(e))
-			err = e
+		v, err := pdRequest(ctx, addr, minResolvedTSPrefix, p.cli, http.MethodGet, bytes.NewBuffer(data))
+		if err != nil {
+			logutil.BgLogger().Debug("failed to get min resolved ts", zap.String("addr", addr), zap.Error(err))
 			continue
 		}
 		logutil.BgLogger().Debug("min resolved ts", zap.String("resp", string(v)))
+		// - When no store is given, cluster-level's min_resolved_ts will be returned,
+		//		and min_resolved_ts for each store will be empty.
+		// - When given a list of stores, min_resolved_ts will be provided for each store
+		//      and the scope-specific min_resolved_ts will be returned.
 		d := struct {
 			IsRealTime          bool              `json:"is_real_time,omitempty"`
 			StoresMinResolvedTS map[uint64]uint64 `json:"stores_min_resolved_ts"`