expression: support functions fromdays and todays push down to ti…

…flash (#34135)

close #34136

expression/expr_to_pb_test.go

@@ -882,6 +882,16 @@ func TestExprPushDownToFlash(t *testing.T) {
 	require.Equal(t, tipb.ScalarFuncSig_ConcatWS, function.(*ScalarFunction).Function.PbCode())
 	exprs = append(exprs, function)
 
+	function, err = NewFunction(mock.NewContext(), ast.FromDays, types.NewFieldType(mysql.TypeDate), intColumn)
+	require.NoError(t, err)
+	require.Equal(t, tipb.ScalarFuncSig_FromDays, function.(*ScalarFunction).Function.PbCode())
+	exprs = append(exprs, function)
+
+	function, err = NewFunction(mock.NewContext(), ast.ToDays, types.NewFieldType(mysql.TypeLonglong), datetimeColumn)
+	require.NoError(t, err)
+	require.Equal(t, tipb.ScalarFuncSig_ToDays, function.(*ScalarFunction).Function.PbCode())
+	exprs = append(exprs, function)
+
 	// StrToDateDateTime
 	function, err = NewFunction(mock.NewContext(), ast.StrToDate, types.NewFieldType(mysql.TypeDatetime), stringColumn, stringColumn)
 	require.NoError(t, err)
@@ -1368,7 +1378,7 @@ func TestExprOnlyPushDownToTiKV(t *testing.T) {
 	sc := new(stmtctx.StatementContext)
 	client := new(mock.Client)
 
-	function, err := NewFunction(mock.NewContext(), "from_days", types.NewFieldType(mysql.TypeLonglong), genColumn(mysql.TypeDatetime, 1))
+	function, err := NewFunction(mock.NewContext(), "uuid", types.NewFieldType(mysql.TypeLonglong))
 	require.NoError(t, err)
 	var exprs = make([]Expression, 0)
 	exprs = append(exprs, function)

expression/expression.go

@@ -1057,6 +1057,7 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 		ast.Date, ast.Year, ast.Month, ast.Day, ast.Quarter, ast.DayName, ast.MonthName,
 		ast.DateDiff, ast.TimestampDiff, ast.DateFormat, ast.FromUnixTime,
 		ast.DayOfWeek, ast.DayOfMonth, ast.DayOfYear, ast.LastDay, ast.WeekOfYear, ast.ToSeconds,
+		ast.FromDays, ast.ToDays,
 
 		ast.Sqrt, ast.Log, ast.Log2, ast.Log10, ast.Ln, ast.Exp, ast.Pow, ast.Sign,
 		ast.Radians, ast.Degrees, ast.Conv, ast.CRC32,