diff --git a/internal/util/indexparamcheck/index_type.go b/internal/util/indexparamcheck/index_type.go
index 17b7d37303..9e1441a176 100644
--- a/internal/util/indexparamcheck/index_type.go
+++ b/internal/util/indexparamcheck/index_type.go
@@ -15,6 +15,7 @@ package indexparamcheck
 type IndexType = string
 
 const (
+	// IndexFaissIDMap represents "FLAT" which means no index is built.
 	IndexFaissIDMap      IndexType = "FLAT"
 	IndexFaissIvfFlat    IndexType = "IVF_FLAT"
 	IndexFaissIvfPQ      IndexType = "IVF_PQ"