diff --git a/internal/querynode/data_sync_service.go b/internal/querynode/data_sync_service.go
index 8ef041d690..ebea45a41b 100644
--- a/internal/querynode/data_sync_service.go
+++ b/internal/querynode/data_sync_service.go
@@ -303,6 +303,7 @@ func newDataSyncService(ctx context.Context,
 	}
 }
 
+// close would close and remove all flow graphs in dataSyncService
 func (dsService *dataSyncService) close() {
 	// close collection flow graphs
 	for _, nodeFGs := range dsService.collectionFlowGraphs {