diff --git a/internal/util/indexparamcheck/conf_adapter.go b/internal/util/indexparamcheck/conf_adapter.go
index 1bf48e9550..a914b4ded3 100644
--- a/internal/util/indexparamcheck/conf_adapter.go
+++ b/internal/util/indexparamcheck/conf_adapter.go
@@ -298,6 +298,7 @@ func newBinIVFConfAdapter() *BinIVFConfAdapter {
 type NSGConfAdapter struct {
 }
 
+// CheckTrain checks if a nsg index can be built with specific parameters.
 func (adapter *NSGConfAdapter) CheckTrain(params map[string]string) bool {
 	if !CheckStrByValues(params, Metric, METRICS) {
 		return false