fix: use max MvccTs for iterator (#37247)

issue: #37158

Signed-off-by: Patrick Weizhi Xu <weizhi.xu@zilliz.com>

internal/proxy/task_query.go

@@ -551,7 +551,7 @@ func (t *queryTask) PostExecute(ctx context.Context) error {
 
 	if t.queryParams.isIterator && t.request.GetGuaranteeTimestamp() == 0 {
 		// first page for iteration, need to set up sessionTs for iterator
-		t.result.SessionTs = t.GetGuaranteeTimestamp()
+		t.result.SessionTs = getMaxMvccTsFromChannels(t.channelsMvcc, t.BeginTs())
 	}
 	log.Debug("Query PostExecute done")
 	return nil

internal/proxy/task_search.go

@@ -745,7 +745,7 @@ func (t *searchTask) PostExecute(ctx context.Context) error {
 	t.result.CollectionName = t.request.GetCollectionName()
 	if t.isIterator && t.request.GetGuaranteeTimestamp() == 0 {
 		// first page for iteration, need to set up sessionTs for iterator
-		t.result.SessionTs = t.SearchRequest.GetGuaranteeTimestamp()
+		t.result.SessionTs = getMaxMvccTsFromChannels(t.queryChannelsTs, t.BeginTs())
 	}
 
 	metrics.ProxyReduceResultLatency.WithLabelValues(strconv.FormatInt(paramtable.GetNodeID(), 10), metrics.SearchLabel).Observe(float64(tr.RecordSpan().Milliseconds()))

internal/proxy/util.go

@@ -1001,6 +1001,22 @@ func parseGuaranteeTs(ts, tMax typeutil.Timestamp) typeutil.Timestamp {
 	return ts
 }
 
+func getMaxMvccTsFromChannels(channelsTs map[string]uint64, beginTs typeutil.Timestamp) typeutil.Timestamp {
+	maxTs := typeutil.Timestamp(0)
+	for _, ts := range channelsTs {
+		if ts > maxTs {
+			maxTs = ts
+		}
+	}
+
+	if maxTs == 0 {
+		log.Warn("no channel ts found, use beginTs instead")
+		return beginTs
+	}
+
+	return maxTs
+}
+
 func validateName(entity string, nameType string) error {
 	entity = strings.TrimSpace(entity)