diff --git a/expression/expr_to_pb_test.go b/expression/expr_to_pb_test.go
index d997e9cf1691f..1a60a1266b8df 100644
--- a/expression/expr_to_pb_test.go
+++ b/expression/expr_to_pb_test.go
@@ -729,14 +729,41 @@ func (s *testEvaluatorSuite) TestExprPushDownToFlash(c *C) {
 	c.Assert(err, IsNil)
 	exprs = append(exprs, function)
 
+	// ScalarFuncSig_RoundReal
 	function, err = NewFunction(mock.NewContext(), ast.Round, types.NewFieldType(mysql.TypeDouble), realColumn)
 	c.Assert(err, IsNil)
 	exprs = append(exprs, function)
 
+	// ScalarFuncSig_RoundInt
 	function, err = NewFunction(mock.NewContext(), ast.Round, types.NewFieldType(mysql.TypeLonglong), intColumn)
 	c.Assert(err, IsNil)
 	exprs = append(exprs, function)
 
+	// concat
+	function, err = NewFunction(mock.NewContext(), ast.Concat, types.NewFieldType(mysql.TypeString), stringColumn, intColumn, realColumn)
+	c.Assert(err, IsNil)
+	exprs = append(exprs, function)
+
+	// UnixTimestampCurrent
+	function, err = NewFunction(mock.NewContext(), ast.UnixTimestamp, types.NewFieldType(mysql.TypeLonglong))
+	c.Assert(err, IsNil)
+	_, ok := function.(*Constant)
+	c.Assert(ok, IsTrue)
+
+	// UnixTimestampInt
+	datetimeColumn.RetType.Decimal = 0
+	function, err = NewFunction(mock.NewContext(), ast.UnixTimestamp, types.NewFieldType(mysql.TypeLonglong), datetimeColumn)
+	c.Assert(err, IsNil)
+	c.Assert(function.(*ScalarFunction).Function.PbCode(), Equals, tipb.ScalarFuncSig_UnixTimestampInt)
+	exprs = append(exprs, function)
+
+	// UnixTimestampDecimal
+	datetimeColumn.RetType.Decimal = types.UnspecifiedLength
+	function, err = NewFunction(mock.NewContext(), ast.UnixTimestamp, types.NewFieldType(mysql.TypeNewDecimal), datetimeColumn)
+	c.Assert(err, IsNil)
+	c.Assert(function.(*ScalarFunction).Function.PbCode(), Equals, tipb.ScalarFuncSig_UnixTimestampDec)
+	exprs = append(exprs, function)
+
 	canPush := CanExprsPushDown(sc, exprs, client, kv.TiFlash)
 	c.Assert(canPush, Equals, true)
 
diff --git a/expression/expression.go b/expression/expression.go
index 20178919a89b4..9a14537cac248 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -1001,6 +1001,7 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 		ast.GE, ast.LE, ast.EQ, ast.NE, ast.LT, ast.GT, ast.In, ast.IsNull, ast.Like,
 		ast.Plus, ast.Minus, ast.Div, ast.Mul, /*ast.Mod,*/
 		ast.If, ast.Ifnull, ast.Case,
+		ast.Concat,
 		ast.Month,
 		ast.TimestampDiff, ast.DateFormat, ast.FromUnixTime,
 		ast.JSONLength:
@@ -1026,6 +1027,11 @@ func scalarExprSupportedByFlash(function *ScalarFunction) bool {
 		case tipb.ScalarFuncSig_AddDateDatetimeInt, tipb.ScalarFuncSig_AddDateStringInt:
 			return true
 		}
+	case ast.UnixTimestamp:
+		switch function.Function.PbCode() {
+		case tipb.ScalarFuncSig_UnixTimestampInt, tipb.ScalarFuncSig_UnixTimestampDec:
+			return true
+		}
 	case ast.Round:
 		switch function.Function.PbCode() {
 		case tipb.ScalarFuncSig_RoundInt, tipb.ScalarFuncSig_RoundReal: