expression: support enum pushdown

executor/builder.go

@@ -1204,6 +1204,12 @@ func (b *executorBuilder) buildHashJoin(v *plannercore.PhysicalHashJoin) Executo
 	} else {
 		e.buildTypes, e.probeTypes = rightTypes, leftTypes
 	}
+	for _, key := range e.buildKeys {
+		e.buildTypes[key.Index].Flag = key.RetType.Flag
+	}
+	for _, key := range e.probeKeys {
+		e.probeTypes[key.Index].Flag = key.RetType.Flag
+	}
 	return e
 }
 

expression/builtin_cast.go

@@ -1840,6 +1840,14 @@ func BuildCastFunction(ctx sessionctx.Context, expr Expression, tp *types.FieldT
 // WrapWithCastAsInt wraps `expr` with `cast` if the return type of expr is not
 // type int, otherwise, returns `expr` directly.
 func WrapWithCastAsInt(ctx sessionctx.Context, expr Expression) Expression {
+	if expr.GetType().Tp == mysql.TypeEnum {
+		if col, ok := expr.(*Column); ok {
+			col = col.Clone().(*Column)
+			col.RetType = col.RetType.Clone()
+			expr = col
+		}
+		expr.GetType().Flag |= mysql.EnumSetAsIntFlag
+	}
 	if expr.GetType().EvalType() == types.ETInt {
 		return expr
 	}

expression/chunk_executor.go

@@ -265,6 +265,14 @@ func executeToInt(ctx sessionctx.Context, expr Expression, fieldType *types.Fiel
 		output.AppendBytes(colID, types.NewBinaryLiteralFromUint(uint64(res), -1))
 		return nil
 	}
+	if fieldType.Tp == mysql.TypeEnum {
+		e, err := types.ParseEnumValue(fieldType.Elems, uint64(res))
+		if err != nil {
+			return err
+		}
+		output.AppendEnum(colID, e)
+		return nil
+	}
 	if mysql.HasUnsignedFlag(fieldType.Flag) {
 		output.AppendUint64(colID, uint64(res))
 		return nil

expression/distsql_builtin.go

@@ -40,6 +40,7 @@ func PbTypeToFieldType(tp *tipb.FieldType) *types.FieldType {
 		Decimal: int(tp.Decimal),
 		Charset: tp.Charset,
 		Collate: protoToCollation(tp.Collate),
+		Elems:   tp.Elems,
 	}
 }
 
@@ -1117,6 +1118,8 @@ func PBToExpr(expr *tipb.Expr, tps []*types.FieldType, sc *stmtctx.StatementCont
 		return convertTime(expr.Val, expr.FieldType, sc.TimeZone)
 	case tipb.ExprType_MysqlJson:
 		return convertJSON(expr.Val)
+	case tipb.ExprType_MysqlEnum:
+		return convertEnum(expr.Val, expr.FieldType)
 	}
 	if expr.Tp != tipb.ExprType_ScalarFunc {
 		panic("should be a tipb.ExprType_ScalarFunc")
@@ -1259,3 +1262,16 @@ func convertJSON(val []byte) (*Constant, error) {
 	}
 	return &Constant{Value: d, RetType: types.NewFieldType(mysql.TypeJSON)}, nil
 }
+
+func convertEnum(val []byte, tp *tipb.FieldType) (*Constant, error) {
+	_, uVal, err := codec.DecodeUint(val)
+	if err != nil {
+		return nil, errors.Errorf("invalid enum % x", val)
+	}
+	e, err := types.ParseEnumValue(tp.Elems, uVal)
+	if err != nil {
+		return nil, err
+	}
+	d := types.NewMysqlEnumDatum(e)
+	return &Constant{Value: d, RetType: FieldTypeFromPB(tp)}, nil
+}

expression/distsql_builtin_test.go

@@ -942,6 +942,7 @@ func toPBFieldType(ft *types.FieldType) *tipb.FieldType {
 		Decimal: int32(ft.Decimal),
 		Charset: ft.Charset,
 		Collate: collationToProto(ft.Collate),
+		Elems:   ft.Elems,
 	}
 }
 

expression/expr_to_pb.go

@@ -141,6 +141,9 @@ func (pc *PbConverter) encodeDatum(ft *types.FieldType, d types.Datum) (tipb.Exp
 			return tp, val, true
 		}
 		return tp, nil, false
+	case types.KindMysqlEnum:
+		tp = tipb.ExprType_MysqlEnum
+		val = codec.EncodeUint(nil, d.GetUint64())
 	default:
 		return tp, nil, false
 	}
@@ -156,6 +159,7 @@ func ToPBFieldType(ft *types.FieldType) *tipb.FieldType {
 		Decimal: int32(ft.Decimal),
 		Charset: ft.Charset,
 		Collate: collationToProto(ft.Collate),
+		Elems:   ft.Elems,
 	}
 }
 
@@ -168,6 +172,7 @@ func FieldTypeFromPB(ft *tipb.FieldType) *types.FieldType {
 		Decimal: int(ft.Decimal),
 		Charset: ft.Charset,
 		Collate: protoToCollation(ft.Collate),
+		Elems:   ft.Elems,
 	}
 }
 
@@ -204,7 +209,7 @@ func (pc PbConverter) columnToPBExpr(column *Column) *tipb.Expr {
 		return nil
 	}
 	switch column.GetType().Tp {
-	case mysql.TypeBit, mysql.TypeSet, mysql.TypeEnum, mysql.TypeGeometry, mysql.TypeUnspecified:
+	case mysql.TypeBit, mysql.TypeSet, mysql.TypeGeometry, mysql.TypeUnspecified:
 		return nil
 	}
 

expression/expr_to_pb_test.go

@@ -144,7 +144,6 @@ func (s *testEvaluatorSuite) TestColumn2Pb(c *C) {
 
 	colExprs = append(colExprs, dg.genColumn(mysql.TypeBit, 1))
 	colExprs = append(colExprs, dg.genColumn(mysql.TypeSet, 2))
-	colExprs = append(colExprs, dg.genColumn(mysql.TypeEnum, 3))
 	colExprs = append(colExprs, dg.genColumn(mysql.TypeGeometry, 4))
 	colExprs = append(colExprs, dg.genColumn(mysql.TypeUnspecified, 5))
 
@@ -180,6 +179,7 @@ func (s *testEvaluatorSuite) TestColumn2Pb(c *C) {
 	colExprs = append(colExprs, dg.genColumn(mysql.TypeBlob, 21))
 	colExprs = append(colExprs, dg.genColumn(mysql.TypeVarString, 22))
 	colExprs = append(colExprs, dg.genColumn(mysql.TypeString, 23))
+	colExprs = append(colExprs, dg.genColumn(mysql.TypeEnum, 24))
 	pushed, remained = PushDownExprs(sc, colExprs, client, kv.UnSpecified)
 	c.Assert(len(pushed), Equals, len(colExprs))
 	c.Assert(len(remained), Equals, 0)
@@ -209,6 +209,7 @@ func (s *testEvaluatorSuite) TestColumn2Pb(c *C) {
 		"{\"tp\":201,\"val\":\"gAAAAAAAABU=\",\"sig\":0,\"field_type\":{\"tp\":252,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":63,\"charset\":\"\"},\"has_distinct\":false}",
 		"{\"tp\":201,\"val\":\"gAAAAAAAABY=\",\"sig\":0,\"field_type\":{\"tp\":253,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":46,\"charset\":\"\"},\"has_distinct\":false}",
 		"{\"tp\":201,\"val\":\"gAAAAAAAABc=\",\"sig\":0,\"field_type\":{\"tp\":254,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":46,\"charset\":\"\"},\"has_distinct\":false}",
+		"{\"tp\":201,\"val\":\"gAAAAAAAABg=\",\"sig\":0,\"field_type\":{\"tp\":247,\"flag\":0,\"flen\":-1,\"decimal\":-1,\"collate\":63,\"charset\":\"\"},\"has_distinct\":false}",
 	}
 	for i, pbExpr := range pbExprs {
 		c.Assert(pbExprs, NotNil)

expression/expression.go

@@ -1153,11 +1153,20 @@ func canScalarFuncPushDown(scalarFunc *ScalarFunction, pc PbConverter, storeType
 }
 
 func canExprPushDown(expr Expression, pc PbConverter, storeType kv.StoreType) bool {
-	if storeType == kv.TiFlash && expr.GetType().Tp == mysql.TypeDuration {
-		if pc.sc.InExplainStmt {
-			pc.sc.AppendWarning(errors.New("Expr '" + expr.String() + "' can not be pushed to TiFlash because it contains Duration type"))
+	if storeType == kv.TiFlash {
+		switch expr.GetType().Tp {
+		case mysql.TypeDuration:
+			if pc.sc.InExplainStmt {
+				pc.sc.AppendWarning(errors.New("Expr '" + expr.String() + "' can not be pushed to TiFlash because it contains Duration type"))
+			}
+			return false
+		case mysql.TypeEnum:
+			if pc.sc.InExplainStmt {
+				pc.sc.AppendWarning(errors.New("Expr '" + expr.String() + "' can not be pushed to TiFlash because it contains Enum type"))
+			}
+			return false
+		default:
 		}
-		return false
 	}
 	switch x := expr.(type) {
 	case *CorrelatedColumn:

expression/integration_test.go

@@ -8985,6 +8985,96 @@ func (s *testIntegrationSuite) TestClusteredIndexCorCol(c *C) {
 	tk.MustQuery("select (select t2.c_str from t2 where t2.c_str = t1.c_str and t2.c_int = 10 order by t2.c_str limit 1) x from t1;").Check(testkit.Rows("<nil>", "goofy mestorf"))
 }
 
+func (s *testIntegrationSuite) TestEnumPushDown(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t")
+	tk.MustExec("create table t (c_enum enum('c', 'b', 'a'))")
+	tk.MustExec("insert into t values ('a'), ('b'), ('c'), ('a'), ('b'), ('a')")
+
+	// test order by
+	tk.MustQuery("select c_enum from t order by c_enum").
+		Check(testkit.Rows("c", "b", "b", "a", "a", "a"))
+	tk.MustQuery("select c_enum from t order by c_enum desc").
+		Check(testkit.Rows("a", "a", "a", "b", "b", "c"))
+	tk.MustQuery("select c_enum from t order by if(c_enum>1, c_enum, c_enum)").
+		Check(testkit.Rows("a", "a", "a", "b", "b", "c"))
+
+	// test selection
+	tk.MustQuery("select c_enum from t where c_enum order by c_enum").
+		Check(testkit.Rows("c", "b", "b", "a", "a", "a"))
+	tk.MustQuery("select c_enum from t where c_enum > 'a' order by c_enum").
+		Check(testkit.Rows("c", "b", "b"))
+	tk.MustQuery("select c_enum from t where c_enum > 1 order by c_enum").
+		Check(testkit.Rows("b", "b", "a", "a", "a"))
+	tk.MustQuery("select c_enum from t where c_enum = 1 order by c_enum").
+		Check(testkit.Rows("c"))
+	tk.MustQuery("select c_enum from t where c_enum = 'a' order by c_enum").
+		Check(testkit.Rows("a", "a", "a"))
+	tk.MustQuery("select c_enum from t where c_enum + 1 order by c_enum").
+		Check(testkit.Rows("c", "b", "b", "a", "a", "a"))
+	tk.MustQuery("select c_enum from t where c_enum - 1 order by c_enum").
+		Check(testkit.Rows("b", "b", "a", "a", "a"))
+
+	// test projection
+	tk.MustQuery("select c_enum+1 from t order by c_enum").
+		Check(testkit.Rows("2", "3", "3", "4", "4", "4"))
+	tk.MustQuery("select c_enum, c_enum=1 from t order by c_enum").
+		Check(testkit.Rows("c 1", "b 0", "b 0", "a 0", "a 0", "a 0"))
+	tk.MustQuery("select c_enum, c_enum>1 from t order by c_enum").
+		Check(testkit.Rows("c 0", "b 1", "b 1", "a 1", "a 1", "a 1"))
+	tk.MustQuery("select c_enum, c_enum>'a' from t order by c_enum").
+		Check(testkit.Rows("c 1", "b 1", "b 1", "a 0", "a 0", "a 0"))
+
+	// test aggregate
+	tk.MustQuery("select max(c_enum) from t").
+		Check(testkit.Rows("c"))
+	tk.MustQuery("select min(c_enum) from t").
+		Check(testkit.Rows("a"))
+	tk.MustQuery("select max(c_enum+1) from t").
+		Check(testkit.Rows("4"))
+	tk.MustQuery("select min(c_enum+1) from t").
+		Check(testkit.Rows("2"))
+	tk.MustQuery("select avg(c_enum) from t").
+		Check(testkit.Rows("2.3333333333333335"))
+	tk.MustQuery("select avg(distinct c_enum) from t").
+		Check(testkit.Rows("2"))
+	tk.MustQuery("select distinct c_enum from t order by c_enum").
+		Check(testkit.Rows("c", "b", "a"))
+	tk.MustQuery("select c_enum from t group by c_enum order by c_enum").
+		Check(testkit.Rows("c", "b", "a"))
+
+	// test correlated
+	tk.MustExec("drop table if exists t1")
+	tk.MustExec(`CREATE TABLE t1 (
+		a char(3) NOT NULL default '',
+		e enum('a','b','c','d','e') NOT NULL default 'a'
+	)`)
+	tk.MustExec("INSERT INTO t1 VALUES ('aaa','e')")
+	tk.MustExec("INSERT INTO t1 VALUES ('bbb','e')")
+	tk.MustExec("INSERT INTO t1 VALUES ('ccc','a')")
+	tk.MustExec("INSERT INTO t1 VALUES ('ddd','e')")
+	tk.MustQuery(`SELECT DISTINCT e AS c FROM t1 outr WHERE
+	a <> SOME ( SELECT a FROM t1 WHERE e = outr.e)`).
+		Check(testkit.Rows("e"))
+
+	// no index
+	tk.MustExec("drop table t")
+	tk.MustExec("create table t(e enum('c','b','a'))")
+	tk.MustExec("insert into t values(1),(2),(3)")
+	tk.MustQuery("select e from t where e > 'b'").
+		Check(testkit.Rows("c"))
+	tk.MustQuery("select e from t where e > 2").
+		Check(testkit.Rows("a"))
+
+	// enable index
+	tk.MustExec("alter table t add index idx(e)")
+	tk.MustQuery("select e from t where e > 'b'").
+		Check(testkit.Rows("c"))
+	tk.MustQuery("select e from t where e > 2").
+		Check(testkit.Rows("a"))
+}
+
 func (s *testIntegrationSuite) TestJiraSetInnoDBDefaultRowFormat(c *C) {
 	// For issue #23541
 	// JIRA needs to be able to set this to be happy.

expression/scalar_function.go

@@ -359,7 +359,13 @@ func (sf *ScalarFunction) Eval(row chunk.Row) (d types.Datum, err error) {
 	case types.ETJson:
 		res, isNull, err = sf.EvalJSON(sf.GetCtx(), row)
 	case types.ETString:
-		res, isNull, err = sf.EvalString(sf.GetCtx(), row)
+		var str string
+		str, isNull, err = sf.EvalString(sf.GetCtx(), row)
+		if !isNull && err == nil && tp.Tp == mysql.TypeEnum {
+			res, err = types.ParseEnumName(tp.Elems, str, tp.Collate)
+		} else {
+			res = str
+		}
 	}
 
 	if isNull || err != nil {

go.mod

@@ -47,7 +47,7 @@ require (
 	github.com/pingcap/goleveldb v0.0.0-20191226122134-f82aafb29989
 	github.com/pingcap/kvproto v0.0.0-20210308063835-39b884695fb8
 	github.com/pingcap/log v0.0.0-20210317133921-96f4fcab92a4
-	github.com/pingcap/parser v0.0.0-20210330190622-f959a136fc19
+	github.com/pingcap/parser v0.0.0-20210421190254-588138d35e55
 	github.com/pingcap/sysutil v0.0.0-20210315073920-cc0985d983a3
 	github.com/pingcap/tidb-tools v4.0.9-0.20201127090955-2707c97b3853+incompatible
 	github.com/pingcap/tipb v0.0.0-20210422074242-57dd881b81b1
@@ -75,7 +75,7 @@ require (
 	golang.org/x/net v0.0.0-20210316092652-d523dce5a7f4
 	golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9
 	golang.org/x/sys v0.0.0-20210324051608-47abb6519492
-	golang.org/x/text v0.3.5
+	golang.org/x/text v0.3.6
 	golang.org/x/tools v0.1.0
 	google.golang.org/grpc v1.27.1
 	gopkg.in/check.v1 v1.0.0-20201130134442-10cb98267c6c // indirect

go.sum

@@ -443,8 +443,8 @@ github.com/pingcap/log v0.0.0-20200511115504-543df19646ad/go.mod h1:4rbK1p9ILyIf
 github.com/pingcap/log v0.0.0-20201112100606-8f1e84a3abc8/go.mod h1:4rbK1p9ILyIfb6hU7OG2CiWSqMXnp3JMbiaVJ6mvoY8=
 github.com/pingcap/log v0.0.0-20210317133921-96f4fcab92a4 h1:ERrF0fTuIOnwfGbt71Ji3DKbOEaP189tjym50u8gpC8=
 github.com/pingcap/log v0.0.0-20210317133921-96f4fcab92a4/go.mod h1:4rbK1p9ILyIfb6hU7OG2CiWSqMXnp3JMbiaVJ6mvoY8=
-github.com/pingcap/parser v0.0.0-20210330190622-f959a136fc19 h1:WQJbP0G8RL9v+rQV7/2UAImJcV6FU9gpJ1fzpyQuaXg=
-github.com/pingcap/parser v0.0.0-20210330190622-f959a136fc19/go.mod h1:xZC8I7bug4GJ5KtHhgAikjTfU4kBv1Sbo3Pf1MZ6lVw=
+github.com/pingcap/parser v0.0.0-20210421190254-588138d35e55 h1:J/NfwCFFPCv7h44ft+2pS3KiMyvOkHprPM5NhDJEoHc=
+github.com/pingcap/parser v0.0.0-20210421190254-588138d35e55/go.mod h1:xZC8I7bug4GJ5KtHhgAikjTfU4kBv1Sbo3Pf1MZ6lVw=
 github.com/pingcap/sysutil v0.0.0-20200206130906-2bfa6dc40bcd/go.mod h1:EB/852NMQ+aRKioCpToQ94Wl7fktV+FNnxf3CX/TTXI=
 github.com/pingcap/sysutil v0.0.0-20210315073920-cc0985d983a3 h1:A9KL9R+lWSVPH8IqUuH1QSTRJ5FGoY1bT2IcfPKsWD8=
 github.com/pingcap/sysutil v0.0.0-20210315073920-cc0985d983a3/go.mod h1:tckvA041UWP+NqYzrJ3fMgC/Hw9wnmQ/tUkp/JaHly8=
@@ -500,6 +500,7 @@ github.com/russross/blackfriday/v2 v2.0.1/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQD
 github.com/sasha-s/go-deadlock v0.2.0/go.mod h1:StQn567HiB1fF2yJ44N9au7wOhrPS3iZqiDbRupzT10=
 github.com/satori/go.uuid v1.2.0/go.mod h1:dA0hQrYB0VpLJoorglMZABFdXlWrHn1NEOzdhQKdks0=
 github.com/sergi/go-diff v1.0.1-0.20180205163309-da645544ed44/go.mod h1:0CfEIISq7TuYL3j771MWULgwwjU+GofnZX9QAmXWZgo=
+github.com/sergi/go-diff v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
 github.com/sergi/go-diff v1.1.0/go.mod h1:STckp+ISIX8hZLjrqAeVduY0gWCT9IjLuqbuNXdaHfM=
 github.com/shirou/gopsutil v2.19.10+incompatible/go.mod h1:5b4v6he4MtMOwMlS0TUMTu2PcXUg8+E1lC7eC3UO/RA=
 github.com/shirou/gopsutil v3.21.2+incompatible h1:U+YvJfjCh6MslYlIAXvPtzhW3YZEtc9uncueUNpD/0A=
@@ -781,8 +782,8 @@ golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.5 h1:i6eZZ+zk0SOf0xgBpEpPD18qWcJda6q1sxt3S0kzyUQ=
-golang.org/x/text v0.3.5/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.6 h1:aRYxNxv6iGQlyVaZmk6ZgYEDa+Jg18DxebPSrd6bg1M=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
 golang.org/x/time v0.0.0-20180412165947-fbb02b2291d2/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20181108054448-85acf8d2951c/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=
 golang.org/x/time v0.0.0-20190308202827-9d24e82272b4/go.mod h1:tRJNPiyCQ0inRvYxbN9jk5I+vvW/OXSQhTDSoE431IQ=

kv/checker.go

@@ -40,7 +40,7 @@ func (d RequestTypeSupportedChecker) supportExpr(exprType tipb.ExprType) bool {
 	switch exprType {
 	case tipb.ExprType_Null, tipb.ExprType_Int64, tipb.ExprType_Uint64, tipb.ExprType_String, tipb.ExprType_Bytes,
 		tipb.ExprType_MysqlDuration, tipb.ExprType_MysqlTime, tipb.ExprType_MysqlDecimal,
-		tipb.ExprType_Float32, tipb.ExprType_Float64, tipb.ExprType_ColumnRef:
+		tipb.ExprType_Float32, tipb.ExprType_Float64, tipb.ExprType_ColumnRef, tipb.ExprType_MysqlEnum:
 		return true
 	// aggregate functions.
 	case tipb.ExprType_Count, tipb.ExprType_First, tipb.ExprType_Max, tipb.ExprType_Min, tipb.ExprType_Sum, tipb.ExprType_Avg,

store/mockstore/unistore/cophandler/closure_exec.go

@@ -810,12 +810,12 @@ func (e *closureExecutor) processSelection(needCollectDetail bool) (gotRow bool,
 		if d.IsNull() {
 			gotRow = false
 		} else {
-			isBool, err := d.ToBool(e.sc)
-			isBool, err = expression.HandleOverflowOnSelection(e.sc, isBool, err)
+			isTrue, err := d.ToBool(e.sc)
+			isTrue, err = expression.HandleOverflowOnSelection(e.sc, isTrue, err)
 			if err != nil {
 				return false, errors.Trace(err)
 			}
-			gotRow = isBool != 0
+			gotRow = isTrue != 0
 		}
 		if !gotRow {
 			if e.sc.WarningCount() > wc {

store/mockstore/unistore/cophandler/topn.go

@@ -17,6 +17,8 @@ import (
 	"container/heap"
 
 	"github.com/pingcap/errors"
+	"github.com/pingcap/parser/mysql"
+	"github.com/pingcap/tidb/expression"
 	"github.com/pingcap/tidb/sessionctx/stmtctx"
 	"github.com/pingcap/tidb/types"
 	tipb "github.com/pingcap/tipb/go-tipb"
@@ -97,10 +99,16 @@ func (t *topNHeap) Less(i, j int) bool {
 		v1 := t.rows[i].key[index]
 		v2 := t.rows[j].key[index]
 
-		ret, err := v1.CompareDatum(t.sc, &v2)
-		if err != nil {
-			t.err = errors.Trace(err)
-			return true
+		var ret int
+		var err error
+		if expression.FieldTypeFromPB(by.GetExpr().GetFieldType()).Tp == mysql.TypeEnum {
+			ret = types.CompareUint64(v1.GetUint64(), v2.GetUint64())
+		} else {
+			ret, err = v1.CompareDatum(t.sc, &v2)
+			if err != nil {
+				t.err = errors.Trace(err)
+				return true
+			}
 		}
 
 		if by.Desc {