diff --git a/expression/expr_to_pb_test.go b/expression/expr_to_pb_test.go
index 3c95869076a5b..30cdf5599181b 100644
--- a/expression/expr_to_pb_test.go
+++ b/expression/expr_to_pb_test.go
@@ -853,10 +853,6 @@ func TestExprPushDownToFlash(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, tipb.ScalarFuncSig_SubDateDatetimeInt, function.(*ScalarFunction).Function.PbCode())
 	exprs = append(exprs, function)
-	function, err = NewFunction(mock.NewContext(), ast.DateSub, types.NewFieldType(mysql.TypeDatetime), stringColumn, intColumn, stringColumn)
-	require.NoError(t, err)
-	require.Equal(t, tipb.ScalarFuncSig_SubDateStringInt, function.(*ScalarFunction).Function.PbCode())
-	exprs = append(exprs, function)
 	function, err = NewFunction(mock.NewContext(), ast.SubDate, types.NewFieldType(mysql.TypeDatetime), datetimeColumn, intColumn, stringColumn)
 	require.NoError(t, err)
 	require.Equal(t, tipb.ScalarFuncSig_SubDateDatetimeInt, function.(*ScalarFunction).Function.PbCode())
diff --git a/expression/expression.go b/expression/expression.go
index e4d589f796194..ac0f813269fff 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -1094,12 +1094,12 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 		}
 	case ast.DateAdd, ast.AddDate:
 		switch function.Function.PbCode() {
-		case tipb.ScalarFuncSig_AddDateDatetimeInt, tipb.ScalarFuncSig_AddDateStringInt, tipb.ScalarFuncSig_AddDateStringReal:
+		case tipb.ScalarFuncSig_AddDateDatetimeInt:
 			return true
 		}
 	case ast.DateSub, ast.SubDate:
 		switch function.Function.PbCode() {
-		case tipb.ScalarFuncSig_SubDateDatetimeInt, tipb.ScalarFuncSig_SubDateStringInt:
+		case tipb.ScalarFuncSig_SubDateDatetimeInt:
 			return true
 		}
 	case ast.UnixTimestamp: