diff --git a/internal/querynode/flow_graph_filter_dm_node.go b/internal/querynode/flow_graph_filter_dm_node.go
index f353724332711ddaf6602d4a2c29d805d1a23502..d2034cf84c9012fa816515c0300b95cf3c31b635 100644
--- a/internal/querynode/flow_graph_filter_dm_node.go
+++ b/internal/querynode/flow_graph_filter_dm_node.go
@@ -104,6 +104,7 @@ func (fdmNode *filterDmNode) Operate(in []flowgraph.Msg) []flowgraph.Msg {
 	return []Msg{res}
 }
 
+// filterInvalidDeleteMessage would filter out invalid delete messages
 func (fdmNode *filterDmNode) filterInvalidDeleteMessage(msg *msgstream.DeleteMsg) *msgstream.DeleteMsg {
 	sp, ctx := trace.StartSpanFromContext(msg.TraceCtx())
 	msg.SetTraceCtx(ctx)