diff --git a/internal/querynode/collection_replica.go b/internal/querynode/collection_replica.go
index 35800a0d40..2f57f0faff 100644
--- a/internal/querynode/collection_replica.go
+++ b/internal/querynode/collection_replica.go
@@ -44,6 +44,7 @@ import (
 // across multiple query nodes, and each query node's collectionReplica will maintain its own part.
 type ReplicaInterface interface {
 	// collection
+	// getCollectionIDs returns all collection ids in the collectionReplica
 	getCollectionIDs() []UniqueID
 	addCollection(collectionID UniqueID, schema *schemapb.CollectionSchema) error
 	removeCollection(collectionID UniqueID) error