diff --git a/Makefile b/Makefile
index 99e787d7ad..2ea7f3ecab 100644
--- a/Makefile
+++ b/Makefile
@@ -90,7 +90,7 @@ check:
 	@echo "vet --shadow"
 	@ go tool vet --shadow . 2>&1 | grep -vE 'Godeps' | awk '{print} END{if(NR>0) {exit 1}}'
 	@echo "golint"
-	@ $(GOLINT) ./... 2>&1 | grep -vE 'LastInsertId|NewLexer' | awk '{print} END{if(NR>0) {exit 1}}'
+	@ $(GOLINT) ./... 2>&1 | grep -vE 'LastInsertId|NewLexer|\.pb\.go' | awk '{print} END{if(NR>0) {exit 1}}'
 	@echo "gofmt (simplify)"
 	@ gofmt -s -l . 2>&1 | grep -vE 'Godeps|parser/parser.go|parser/scanner.go' | awk '{print} END{if(NR>0) {exit 1}}'
 
diff --git a/xapi/tipb/expression.pb.go b/xapi/tipb/expression.pb.go
new file mode 100644
index 0000000000..0f008cec04
--- /dev/null
+++ b/xapi/tipb/expression.pb.go
@@ -0,0 +1,458 @@
+// Code generated by protoc-gen-go.
+// source: expression.proto
+// DO NOT EDIT!
+
+/*
+Package tipb is a generated protocol buffer package.
+
+It is generated from these files:
+	expression.proto
+	schema.proto
+	select.proto
+
+It has these top-level messages:
+	Expr
+	TableInfo
+	ColumnInfo
+	IndexInfo
+	KeyRange
+	ByItem
+	SelectRequest
+	Row
+	Error
+	SelectResponse
+*/
+package tipb
+
+import proto "github.com/golang/protobuf/proto"
+import fmt "fmt"
+import math "math"
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// This is a compile-time assertion to ensure that this generated file
+// is compatible with the proto package it is being compiled against.
+const _ = proto.ProtoPackageIsVersion1
+
+type ExprType int32
+
+const (
+	// Values are encoded bytes.
+	ExprType_Null    ExprType = 0
+	ExprType_Int64   ExprType = 1
+	ExprType_Uint64  ExprType = 2
+	ExprType_Float32 ExprType = 3
+	ExprType_Float64 ExprType = 4
+	ExprType_String  ExprType = 5
+	ExprType_Bytes   ExprType = 6
+	// Mysql specific types.
+	ExprType_MysqlBit      ExprType = 101
+	ExprType_MysqlDecimal  ExprType = 102
+	ExprType_MysqlDuration ExprType = 103
+	ExprType_MysqlEnum     ExprType = 104
+	ExprType_MysqlHex      ExprType = 105
+	ExprType_MysqlSet      ExprType = 106
+	ExprType_MysqlTime     ExprType = 107
+	// Column reference. value is int64 column ID.
+	ExprType_ColumnRef ExprType = 201
+	// Unary operations, children count 1.
+	ExprType_Not    ExprType = 1001
+	ExprType_Neg    ExprType = 1002
+	ExprType_BitNeg ExprType = 1003
+	// Comparison operations.
+	ExprType_LT     ExprType = 2001
+	ExprType_LE     ExprType = 2002
+	ExprType_EQ     ExprType = 2003
+	ExprType_NE     ExprType = 2004
+	ExprType_GE     ExprType = 2005
+	ExprType_GT     ExprType = 2006
+	ExprType_NullEQ ExprType = 2007
+	// Bit operations.
+	ExprType_BitAnd    ExprType = 2101
+	ExprType_BitOr     ExprType = 2102
+	ExprType_BitXor    ExprType = 2103
+	ExprType_LeftShift ExprType = 2104
+	ExprType_RighShift ExprType = 2105
+	// Arithmatic.
+	ExprType_Plus   ExprType = 2201
+	ExprType_Minus  ExprType = 2202
+	ExprType_Mul    ExprType = 2203
+	ExprType_Div    ExprType = 2204
+	ExprType_IntDiv ExprType = 2205
+	ExprType_Mod    ExprType = 2206
+	// Logic operations.
+	ExprType_And ExprType = 2301
+	ExprType_Or  ExprType = 2302
+	ExprType_Xor ExprType = 2303
+	// Aggregate functions.
+	ExprType_Count       ExprType = 3001
+	ExprType_Sum         ExprType = 3002
+	ExprType_Avg         ExprType = 3003
+	ExprType_Min         ExprType = 3004
+	ExprType_Max         ExprType = 3005
+	ExprType_First       ExprType = 3006
+	ExprType_GroupConcat ExprType = 3007
+	// Math functions.
+	ExprType_Abs ExprType = 3101
+	ExprType_Pow ExprType = 3102
+	// String functions.
+	ExprType_Concat         ExprType = 3201
+	ExprType_ConcatWS       ExprType = 3202
+	ExprType_Left           ExprType = 3203
+	ExprType_Length         ExprType = 3204
+	ExprType_Lower          ExprType = 3205
+	ExprType_Repeat         ExprType = 3206
+	ExprType_Replace        ExprType = 3207
+	ExprType_Upper          ExprType = 3208
+	ExprType_Strcmp         ExprType = 3209
+	ExprType_Convert        ExprType = 3210
+	ExprType_Cast           ExprType = 3211
+	ExprType_Substring      ExprType = 3212
+	ExprType_SubstringIndex ExprType = 3213
+	ExprType_Locate         ExprType = 3214
+	ExprType_Trim           ExprType = 3215
+	// Control flow functions.
+	ExprType_If     ExprType = 3301
+	ExprType_NullIf ExprType = 3302
+	ExprType_IfNull ExprType = 3303
+	// Time functions.
+	ExprType_Date        ExprType = 3401
+	ExprType_DateAdd     ExprType = 3402
+	ExprType_DateSub     ExprType = 3403
+	ExprType_Year        ExprType = 3411
+	ExprType_YearWeek    ExprType = 3412
+	ExprType_Month       ExprType = 3421
+	ExprType_Week        ExprType = 3431
+	ExprType_Weekday     ExprType = 3432
+	ExprType_WeekOfYear  ExprType = 3433
+	ExprType_Day         ExprType = 3441
+	ExprType_DayName     ExprType = 3442
+	ExprType_DayOfYear   ExprType = 3443
+	ExprType_DayOfMonth  ExprType = 3444
+	ExprType_DayOfWeek   ExprType = 3445
+	ExprType_Hour        ExprType = 3451
+	ExprType_Minute      ExprType = 3452
+	ExprType_Second      ExprType = 3453
+	ExprType_Microsecond ExprType = 3454
+	ExprType_Extract     ExprType = 3461
+	// Other functions;
+	ExprType_Coalesce ExprType = 3501
+	// Other expressions.
+	ExprType_In      ExprType = 4001
+	ExprType_IsTruth ExprType = 4002
+	ExprType_IsNull  ExprType = 4003
+	ExprType_ExprRow ExprType = 4004
+	ExprType_Like    ExprType = 4005
+	ExprType_RLike   ExprType = 4006
+	ExprType_Case    ExprType = 4007
+)
+
+var ExprType_name = map[int32]string{
+	0:    "Null",
+	1:    "Int64",
+	2:    "Uint64",
+	3:    "Float32",
+	4:    "Float64",
+	5:    "String",
+	6:    "Bytes",
+	101:  "MysqlBit",
+	102:  "MysqlDecimal",
+	103:  "MysqlDuration",
+	104:  "MysqlEnum",
+	105:  "MysqlHex",
+	106:  "MysqlSet",
+	107:  "MysqlTime",
+	201:  "ColumnRef",
+	1001: "Not",
+	1002: "Neg",
+	1003: "BitNeg",
+	2001: "LT",
+	2002: "LE",
+	2003: "EQ",
+	2004: "NE",
+	2005: "GE",
+	2006: "GT",
+	2007: "NullEQ",
+	2101: "BitAnd",
+	2102: "BitOr",
+	2103: "BitXor",
+	2104: "LeftShift",
+	2105: "RighShift",
+	2201: "Plus",
+	2202: "Minus",
+	2203: "Mul",
+	2204: "Div",
+	2205: "IntDiv",
+	2206: "Mod",
+	2301: "And",
+	2302: "Or",
+	2303: "Xor",
+	3001: "Count",
+	3002: "Sum",
+	3003: "Avg",
+	3004: "Min",
+	3005: "Max",
+	3006: "First",
+	3007: "GroupConcat",
+	3101: "Abs",
+	3102: "Pow",
+	3201: "Concat",
+	3202: "ConcatWS",
+	3203: "Left",
+	3204: "Length",
+	3205: "Lower",
+	3206: "Repeat",
+	3207: "Replace",
+	3208: "Upper",
+	3209: "Strcmp",
+	3210: "Convert",
+	3211: "Cast",
+	3212: "Substring",
+	3213: "SubstringIndex",
+	3214: "Locate",
+	3215: "Trim",
+	3301: "If",
+	3302: "NullIf",
+	3303: "IfNull",
+	3401: "Date",
+	3402: "DateAdd",
+	3403: "DateSub",
+	3411: "Year",
+	3412: "YearWeek",
+	3421: "Month",
+	3431: "Week",
+	3432: "Weekday",
+	3433: "WeekOfYear",
+	3441: "Day",
+	3442: "DayName",
+	3443: "DayOfYear",
+	3444: "DayOfMonth",
+	3445: "DayOfWeek",
+	3451: "Hour",
+	3452: "Minute",
+	3453: "Second",
+	3454: "Microsecond",
+	3461: "Extract",
+	3501: "Coalesce",
+	4001: "In",
+	4002: "IsTruth",
+	4003: "IsNull",
+	4004: "ExprRow",
+	4005: "Like",
+	4006: "RLike",
+	4007: "Case",
+}
+var ExprType_value = map[string]int32{
+	"Null":           0,
+	"Int64":          1,
+	"Uint64":         2,
+	"Float32":        3,
+	"Float64":        4,
+	"String":         5,
+	"Bytes":          6,
+	"MysqlBit":       101,
+	"MysqlDecimal":   102,
+	"MysqlDuration":  103,
+	"MysqlEnum":      104,
+	"MysqlHex":       105,
+	"MysqlSet":       106,
+	"MysqlTime":      107,
+	"ColumnRef":      201,
+	"Not":            1001,
+	"Neg":            1002,
+	"BitNeg":         1003,
+	"LT":             2001,
+	"LE":             2002,
+	"EQ":             2003,
+	"NE":             2004,
+	"GE":             2005,
+	"GT":             2006,
+	"NullEQ":         2007,
+	"BitAnd":         2101,
+	"BitOr":          2102,
+	"BitXor":         2103,
+	"LeftShift":      2104,
+	"RighShift":      2105,
+	"Plus":           2201,
+	"Minus":          2202,
+	"Mul":            2203,
+	"Div":            2204,
+	"IntDiv":         2205,
+	"Mod":            2206,
+	"And":            2301,
+	"Or":             2302,
+	"Xor":            2303,
+	"Count":          3001,
+	"Sum":            3002,
+	"Avg":            3003,
+	"Min":            3004,
+	"Max":            3005,
+	"First":          3006,
+	"GroupConcat":    3007,
+	"Abs":            3101,
+	"Pow":            3102,
+	"Concat":         3201,
+	"ConcatWS":       3202,
+	"Left":           3203,
+	"Length":         3204,
+	"Lower":          3205,
+	"Repeat":         3206,
+	"Replace":        3207,
+	"Upper":          3208,
+	"Strcmp":         3209,
+	"Convert":        3210,
+	"Cast":           3211,
+	"Substring":      3212,
+	"SubstringIndex": 3213,
+	"Locate":         3214,
+	"Trim":           3215,
+	"If":             3301,
+	"NullIf":         3302,
+	"IfNull":         3303,
+	"Date":           3401,
+	"DateAdd":        3402,
+	"DateSub":        3403,
+	"Year":           3411,
+	"YearWeek":       3412,
+	"Month":          3421,
+	"Week":           3431,
+	"Weekday":        3432,
+	"WeekOfYear":     3433,
+	"Day":            3441,
+	"DayName":        3442,
+	"DayOfYear":      3443,
+	"DayOfMonth":     3444,
+	"DayOfWeek":      3445,
+	"Hour":           3451,
+	"Minute":         3452,
+	"Second":         3453,
+	"Microsecond":    3454,
+	"Extract":        3461,
+	"Coalesce":       3501,
+	"In":             4001,
+	"IsTruth":        4002,
+	"IsNull":         4003,
+	"ExprRow":        4004,
+	"Like":           4005,
+	"RLike":          4006,
+	"Case":           4007,
+}
+
+func (x ExprType) Enum() *ExprType {
+	p := new(ExprType)
+	*p = x
+	return p
+}
+func (x ExprType) String() string {
+	return proto.EnumName(ExprType_name, int32(x))
+}
+func (x *ExprType) UnmarshalJSON(data []byte) error {
+	value, err := proto.UnmarshalJSONEnum(ExprType_value, data, "ExprType")
+	if err != nil {
+		return err
+	}
+	*x = ExprType(value)
+	return nil
+}
+func (ExprType) EnumDescriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
+
+// Evaluators should implement evaluation functions for every expression type.
+type Expr struct {
+	Tp               *ExprType `protobuf:"varint,1,opt,name=tp,enum=tipb.ExprType" json:"tp,omitempty"`
+	Val              []byte    `protobuf:"bytes,2,opt,name=val" json:"val,omitempty"`
+	Children         []*Expr   `protobuf:"bytes,3,rep,name=children" json:"children,omitempty"`
+	XXX_unrecognized []byte    `json:"-"`
+}
+
+func (m *Expr) Reset()                    { *m = Expr{} }
+func (m *Expr) String() string            { return proto.CompactTextString(m) }
+func (*Expr) ProtoMessage()               {}
+func (*Expr) Descriptor() ([]byte, []int) { return fileDescriptor0, []int{0} }
+
+func (m *Expr) GetTp() ExprType {
+	if m != nil && m.Tp != nil {
+		return *m.Tp
+	}
+	return ExprType_Null
+}
+
+func (m *Expr) GetVal() []byte {
+	if m != nil {
+		return m.Val
+	}
+	return nil
+}
+
+func (m *Expr) GetChildren() []*Expr {
+	if m != nil {
+		return m.Children
+	}
+	return nil
+}
+
+func init() {
+	proto.RegisterType((*Expr)(nil), "tipb.Expr")
+	proto.RegisterEnum("tipb.ExprType", ExprType_name, ExprType_value)
+}
+
+var fileDescriptor0 = []byte{
+	// 865 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x44, 0x54, 0x49, 0x70, 0x1b, 0x55,
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+	0xb8, 0x5e, 0x66, 0x24, 0xfb, 0xf0, 0x4b, 0x19, 0x9b, 0x5e, 0xc0, 0x5e, 0x88, 0xfc, 0x5a, 0x76,
+	0xca, 0x62, 0x6e, 0xb7, 0x0b, 0x5f, 0xaf, 0x32, 0x68, 0xc0, 0x37, 0x0c, 0x1a, 0xf7, 0xc3, 0x15,
+	0x06, 0x7b, 0x0d, 0xb8, 0xca, 0xe0, 0x74, 0x03, 0xbe, 0xcd, 0x41, 0x17, 0xbe, 0x5b, 0xa5, 0x14,
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+	0x08, 0x5e, 0x61, 0xb4, 0xa3, 0x46, 0xf0, 0x6a, 0x95, 0xf2, 0xe2, 0x66, 0x88, 0x1c, 0xe5, 0x02,
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+	0xca, 0xa4, 0x16, 0x3e, 0x5f, 0xc3, 0xbd, 0x2d, 0x9d, 0x36, 0x3a, 0x4b, 0xb6, 0x75, 0x1c, 0xf8,
+	0x16, 0xbe, 0xc8, 0x63, 0x0f, 0x52, 0x38, 0xaa, 0x11, 0xda, 0xd7, 0x17, 0xe0, 0x52, 0x8d, 0x3a,
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+	0xd2, 0xc0, 0x45, 0x76, 0xb4, 0x65, 0x22, 0x31, 0xfe, 0x09, 0x17, 0x17, 0x5d, 0x46, 0x12, 0xf9,
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+	0x43, 0x3c, 0xa6, 0xe7, 0xf3, 0x56, 0x34, 0xf6, 0x28, 0xe1, 0x05, 0x0e, 0xee, 0x1a, 0x35, 0x84,
+	0x17, 0x5d, 0x1a, 0x61, 0xb3, 0x07, 0x3f, 0xba, 0x37, 0x57, 0x8d, 0xe4, 0x27, 0x26, 0xcd, 0x1e,
+	0x7f, 0x1f, 0xd7, 0x58, 0xbd, 0x43, 0x81, 0x97, 0x3d, 0xea, 0x81, 0xe0, 0x66, 0x18, 0xc2, 0x97,
+	0x33, 0x86, 0xc5, 0xe0, 0x2b, 0x8f, 0x64, 0x0f, 0x4a, 0xdf, 0xc0, 0x15, 0x8f, 0x26, 0x42, 0xf0,
+	0xbc, 0x94, 0x87, 0x70, 0xd5, 0xe3, 0x3d, 0xeb, 0x18, 0xa7, 0xf0, 0x03, 0xab, 0xd8, 0x7c, 0x8d,
+	0xc3, 0x09, 0x86, 0xfe, 0x04, 0x7e, 0xf6, 0x9c, 0x55, 0x21, 0x88, 0x9d, 0xed, 0x71, 0x92, 0xeb,
+	0x1e, 0xdf, 0x01, 0xba, 0x7e, 0x9b, 0xd6, 0x99, 0xec, 0xf9, 0x78, 0xf9, 0xbf, 0x7b, 0xf4, 0x5c,
+	0x64, 0x53, 0xdd, 0x1f, 0x1c, 0xc8, 0x3c, 0x2f, 0xf1, 0xe7, 0x2d, 0x01, 0xd7, 0xf9, 0x8b, 0x4b,
+	0x9e, 0xd1, 0x99, 0x81, 0xbf, 0x3d, 0x7a, 0x17, 0x5d, 0x1c, 0x3e, 0xe6, 0x1f, 0x26, 0x1d, 0x19,
+	0x68, 0x3a, 0x25, 0x8f, 0xf6, 0xde, 0x52, 0x81, 0xd1, 0x69, 0x6e, 0xb9, 0xc1, 0x55, 0x1b, 0x63,
+	0x6b, 0xfc, 0xc0, 0xc2, 0xc5, 0xe3, 0xf9, 0x92, 0xfd, 0x48, 0xa6, 0xb8, 0xa5, 0x77, 0x8f, 0xf3,
+	0xd8, 0x62, 0x78, 0xad, 0x4e, 0xaa, 0x66, 0xda, 0x35, 0x19, 0x96, 0x7e, 0xbd, 0xce, 0x73, 0x4b,
+	0x79, 0x6e, 0x6f, 0xd4, 0xf3, 0x04, 0x89, 0x69, 0xe3, 0xc9, 0xbc, 0x59, 0xe7, 0xb3, 0x50, 0x87,
+	0x12, 0xde, 0xaa, 0xd3, 0x3c, 0xda, 0x8c, 0xdf, 0xae, 0x4f, 0xf7, 0x28, 0xe1, 0x9d, 0xfa, 0x96,
+	0x2b, 0xee, 0x08, 0xf4, 0x70, 0x3d, 0xc1, 0xb5, 0x05, 0x7e, 0x82, 0x3f, 0xae, 0xf0, 0x80, 0xff,
+	0x5e, 0xfb, 0x85, 0xff, 0x03, 0x00, 0x00, 0xff, 0xff, 0xc0, 0x46, 0xd6, 0x7c, 0x22, 0x05, 0x00,
+	0x00,
+}
diff --git a/xapi/tipb/expression.proto b/xapi/tipb/expression.proto
new file mode 100644
index 0000000000..09f95b9dc4
--- /dev/null
+++ b/xapi/tipb/expression.proto
@@ -0,0 +1,147 @@
+syntax = "proto2";
+
+package tipb;
+
+option java_multiple_files = true;
+option java_package = "com.pingcap.tidb.tipb";
+
+enum ExprType {
+	/* Children count 0. */
+	// Values are encoded bytes.
+	Null = 0;
+	Int64 = 1;
+	Uint64 = 2;
+	Float32 = 3;
+	Float64 = 4;
+	String = 5;
+	Bytes = 6;
+
+	// Mysql specific types.
+	MysqlBit = 101;
+	MysqlDecimal = 102;
+	MysqlDuration = 103;
+	MysqlEnum = 104;
+	MysqlHex = 105;
+	MysqlSet = 106;
+	MysqlTime = 107;
+
+	// Column reference. value is int64 column ID.
+	ColumnRef = 201;
+
+	/* Unary operations, children count 1. */
+	Not = 1001;
+	Neg = 1002;
+	BitNeg = 1003;
+
+	/* Binary operations, children count 2. */
+	// Comparison operations.
+	LT = 2001;
+	LE = 2002;
+	EQ = 2003;
+	NE = 2004;
+	GE = 2005;
+	GT = 2006;
+	NullEQ = 2007;
+
+	// Bit operations.
+	BitAnd = 2101;
+	BitOr = 2102;
+	BitXor = 2103;
+	LeftShift = 2104;
+	RighShift = 2105;
+
+	// Arithmatic.
+	Plus = 2201;
+	Minus = 2202;
+	Mul = 2203;
+	Div = 2204;
+	IntDiv = 2205;
+	Mod = 2206;
+
+	// Logic operations.
+	And = 2301;
+	Or = 2302;
+	Xor = 2303;
+
+	/* Mysql functions, children count is function specific. */
+	// Aggregate functions.
+	Count = 3001;
+	Sum = 3002;
+	Avg = 3003;
+	Min = 3004;
+	Max = 3005;
+	First = 3006;
+	GroupConcat = 3007;
+
+	// Math functions.
+	Abs = 3101;
+	Pow = 3102;
+
+	// String functions.
+	Concat = 3201;
+	ConcatWS = 3202;
+	Left = 3203;
+	Length = 3204;
+	Lower = 3205;
+	Repeat = 3206;
+	Replace = 3207;
+	Upper = 3208;
+	Strcmp = 3209;
+	Convert = 3210;
+	Cast = 3211;
+	Substring = 3212;
+	SubstringIndex = 3213;
+	Locate = 3214;
+	Trim = 3215;
+
+	// Control flow functions.
+	If = 3301;
+	NullIf = 3302;
+	IfNull = 3303;
+
+	// Time functions.
+	Date = 3401;
+	DateAdd = 3402;
+	DateSub = 3403;
+
+	Year = 3411;
+	YearWeek = 3412;
+
+	Month = 3421;
+
+	Week = 3431;
+	Weekday = 3432;
+	WeekOfYear = 3433;
+
+	Day = 3441;
+	DayName = 3442;
+	DayOfYear = 3443;
+	DayOfMonth = 3444;
+	DayOfWeek = 3445;
+
+	Hour = 3451;
+	Minute = 3452;
+	Second = 3453;
+	Microsecond = 3454;
+
+	Extract = 3461;
+
+	// Other functions;
+	Coalesce = 3501;
+
+	/* Other expressions. */
+	In = 4001;
+	IsTruth = 4002;
+	IsNull = 4003;
+	ExprRow = 4004;
+	Like = 4005;
+	RLike = 4006;
+	Case = 4007;
+}
+
+// Evaluators should implement evaluation functions for every expression type.
+message Expr {
+	optional ExprType tp = 1;
+	optional bytes val = 2;
+	repeated Expr children = 3;
+}
diff --git a/xapi/tipb/schema.pb.go b/xapi/tipb/schema.pb.go
new file mode 100644
index 0000000000..05afa2d0c1
--- /dev/null
+++ b/xapi/tipb/schema.pb.go
@@ -0,0 +1,179 @@
+// Code generated by protoc-gen-go.
+// source: schema.proto
+// DO NOT EDIT!
+
+package tipb
+
+import proto "github.com/golang/protobuf/proto"
+import fmt "fmt"
+import math "math"
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+type TableInfo struct {
+	TableId          *int64        `protobuf:"varint,1,opt,name=table_id" json:"table_id,omitempty"`
+	Columns          []*ColumnInfo `protobuf:"bytes,2,rep,name=columns" json:"columns,omitempty"`
+	XXX_unrecognized []byte        `json:"-"`
+}
+
+func (m *TableInfo) Reset()                    { *m = TableInfo{} }
+func (m *TableInfo) String() string            { return proto.CompactTextString(m) }
+func (*TableInfo) ProtoMessage()               {}
+func (*TableInfo) Descriptor() ([]byte, []int) { return fileDescriptor1, []int{0} }
+
+func (m *TableInfo) GetTableId() int64 {
+	if m != nil && m.TableId != nil {
+		return *m.TableId
+	}
+	return 0
+}
+
+func (m *TableInfo) GetColumns() []*ColumnInfo {
+	if m != nil {
+		return m.Columns
+	}
+	return nil
+}
+
+type ColumnInfo struct {
+	ColumnId         *int64   `protobuf:"varint,1,opt,name=column_id" json:"column_id,omitempty"`
+	Tp               *int32   `protobuf:"varint,2,opt,name=tp" json:"tp,omitempty"`
+	Collation        *int32   `protobuf:"varint,3,opt,name=collation" json:"collation,omitempty"`
+	ColumnLen        *int32   `protobuf:"varint,4,opt,name=columnLen" json:"columnLen,omitempty"`
+	Decimal          *int32   `protobuf:"varint,5,opt,name=decimal" json:"decimal,omitempty"`
+	Flag             *int32   `protobuf:"varint,6,opt,name=flag" json:"flag,omitempty"`
+	Elems            []string `protobuf:"bytes,7,rep,name=elems" json:"elems,omitempty"`
+	PkHandle         *bool    `protobuf:"varint,21,opt,name=pk_handle" json:"pk_handle,omitempty"`
+	XXX_unrecognized []byte   `json:"-"`
+}
+
+func (m *ColumnInfo) Reset()                    { *m = ColumnInfo{} }
+func (m *ColumnInfo) String() string            { return proto.CompactTextString(m) }
+func (*ColumnInfo) ProtoMessage()               {}
+func (*ColumnInfo) Descriptor() ([]byte, []int) { return fileDescriptor1, []int{1} }
+
+func (m *ColumnInfo) GetColumnId() int64 {
+	if m != nil && m.ColumnId != nil {
+		return *m.ColumnId
+	}
+	return 0
+}
+
+func (m *ColumnInfo) GetTp() int32 {
+	if m != nil && m.Tp != nil {
+		return *m.Tp
+	}
+	return 0
+}
+
+func (m *ColumnInfo) GetCollation() int32 {
+	if m != nil && m.Collation != nil {
+		return *m.Collation
+	}
+	return 0
+}
+
+func (m *ColumnInfo) GetColumnLen() int32 {
+	if m != nil && m.ColumnLen != nil {
+		return *m.ColumnLen
+	}
+	return 0
+}
+
+func (m *ColumnInfo) GetDecimal() int32 {
+	if m != nil && m.Decimal != nil {
+		return *m.Decimal
+	}
+	return 0
+}
+
+func (m *ColumnInfo) GetFlag() int32 {
+	if m != nil && m.Flag != nil {
+		return *m.Flag
+	}
+	return 0
+}
+
+func (m *ColumnInfo) GetElems() []string {
+	if m != nil {
+		return m.Elems
+	}
+	return nil
+}
+
+func (m *ColumnInfo) GetPkHandle() bool {
+	if m != nil && m.PkHandle != nil {
+		return *m.PkHandle
+	}
+	return false
+}
+
+type IndexInfo struct {
+	TableId          *int64        `protobuf:"varint,1,opt,name=table_id" json:"table_id,omitempty"`
+	IndexId          *int64        `protobuf:"varint,2,opt,name=index_id" json:"index_id,omitempty"`
+	Columns          []*ColumnInfo `protobuf:"bytes,3,rep,name=columns" json:"columns,omitempty"`
+	Unique           *bool         `protobuf:"varint,4,opt,name=unique" json:"unique,omitempty"`
+	XXX_unrecognized []byte        `json:"-"`
+}
+
+func (m *IndexInfo) Reset()                    { *m = IndexInfo{} }
+func (m *IndexInfo) String() string            { return proto.CompactTextString(m) }
+func (*IndexInfo) ProtoMessage()               {}
+func (*IndexInfo) Descriptor() ([]byte, []int) { return fileDescriptor1, []int{2} }
+
+func (m *IndexInfo) GetTableId() int64 {
+	if m != nil && m.TableId != nil {
+		return *m.TableId
+	}
+	return 0
+}
+
+func (m *IndexInfo) GetIndexId() int64 {
+	if m != nil && m.IndexId != nil {
+		return *m.IndexId
+	}
+	return 0
+}
+
+func (m *IndexInfo) GetColumns() []*ColumnInfo {
+	if m != nil {
+		return m.Columns
+	}
+	return nil
+}
+
+func (m *IndexInfo) GetUnique() bool {
+	if m != nil && m.Unique != nil {
+		return *m.Unique
+	}
+	return false
+}
+
+func init() {
+	proto.RegisterType((*TableInfo)(nil), "tipb.TableInfo")
+	proto.RegisterType((*ColumnInfo)(nil), "tipb.ColumnInfo")
+	proto.RegisterType((*IndexInfo)(nil), "tipb.IndexInfo")
+}
+
+var fileDescriptor1 = []byte{
+	// 249 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x74, 0x8f, 0x3d, 0x4f, 0xc3, 0x30,
+	0x10, 0x86, 0x95, 0xaf, 0x26, 0x39, 0x0a, 0x14, 0x4b, 0x95, 0xcc, 0x56, 0x32, 0x65, 0xca, 0xc0,
+	0x2f, 0x40, 0x30, 0x55, 0x62, 0x60, 0x60, 0xaf, 0x1c, 0xfb, 0xda, 0x5a, 0xf8, 0x0b, 0xe2, 0x48,
+	0xfc, 0x0e, 0x7e, 0x31, 0xb6, 0x41, 0x2a, 0x42, 0x30, 0xbe, 0xcf, 0xdd, 0x73, 0xba, 0x17, 0x96,
+	0x13, 0x3f, 0xa2, 0x66, 0x83, 0x7b, 0xb3, 0xde, 0x92, 0xd2, 0x4b, 0x37, 0x76, 0x77, 0xd0, 0x3e,
+	0xb3, 0x51, 0xe1, 0xd6, 0xec, 0x2d, 0x59, 0x41, 0xe3, 0x63, 0xd8, 0x49, 0x41, 0xb3, 0x4d, 0xd6,
+	0x17, 0xe4, 0x06, 0x6a, 0x6e, 0xd5, 0xac, 0xcd, 0x44, 0xf3, 0x4d, 0xd1, 0x9f, 0xdd, 0xae, 0x86,
+	0xa8, 0x0d, 0x0f, 0x09, 0x46, 0xa9, 0xfb, 0xc8, 0x00, 0x4e, 0x91, 0x5c, 0x41, 0xfb, 0x65, 0x9c,
+	0x8e, 0x00, 0xe4, 0xde, 0x05, 0x3f, 0xeb, 0xab, 0xef, 0xb1, 0x62, 0x5e, 0x5a, 0x43, 0x8b, 0x1f,
+	0x28, 0x18, 0x8f, 0x68, 0x68, 0x99, 0xd0, 0x25, 0xd4, 0x02, 0xb9, 0xd4, 0x4c, 0xd1, 0x2a, 0x81,
+	0x25, 0x94, 0x7b, 0xc5, 0x0e, 0x74, 0x91, 0xd2, 0x39, 0x54, 0xa8, 0x50, 0x4f, 0xb4, 0x0e, 0x3f,
+	0xb5, 0xf1, 0x80, 0x7b, 0xd9, 0x1d, 0x99, 0x11, 0x0a, 0xe9, 0x3a, 0x6c, 0x34, 0xdd, 0x08, 0xed,
+	0xd6, 0x08, 0x7c, 0xff, 0xa7, 0x56, 0x20, 0x32, 0x8e, 0x23, 0xc9, 0x7f, 0x17, 0x2d, 0xfe, 0x2e,
+	0x4a, 0x2e, 0x60, 0x31, 0x1b, 0xf9, 0x3a, 0x63, 0x7a, 0xb2, 0xb9, 0xbf, 0x86, 0x35, 0xb7, 0x7a,
+	0x70, 0xd2, 0x1c, 0x38, 0x73, 0x61, 0x5d, 0x8c, 0xc9, 0x79, 0xca, 0x3e, 0x03, 0x00, 0x00, 0xff,
+	0xff, 0xca, 0x33, 0x46, 0xc7, 0x6a, 0x01, 0x00, 0x00,
+}
diff --git a/xapi/tipb/schema.proto b/xapi/tipb/schema.proto
new file mode 100644
index 0000000000..9dc95135f3
--- /dev/null
+++ b/xapi/tipb/schema.proto
@@ -0,0 +1,29 @@
+syntax = "proto2";
+
+package tipb;
+
+option java_multiple_files = true;
+option java_package = "com.pingcap.tidb.tipb";
+
+message TableInfo {
+	optional int64 table_id = 1;
+	repeated ColumnInfo columns = 2;
+}
+
+message ColumnInfo {
+	optional int64 column_id = 1;
+	optional int32 tp = 2; // MySQL type.
+	optional int32 collation = 3;
+	optional int32 columnLen = 4;
+	optional int32 decimal = 5;
+	optional int32 flag = 6;
+	repeated string elems = 7;
+	optional bool pk_handle = 21; // PK handle column value is row handle.
+}
+
+message IndexInfo {
+	optional int64 table_id = 1;
+	optional int64 index_id = 2;
+	repeated ColumnInfo columns = 3;
+	optional bool unique = 4;
+}
diff --git a/xapi/tipb/select.pb.go b/xapi/tipb/select.pb.go
new file mode 100644
index 0000000000..1e66b6ed84
--- /dev/null
+++ b/xapi/tipb/select.pb.go
@@ -0,0 +1,302 @@
+// Code generated by protoc-gen-go.
+// source: select.proto
+// DO NOT EDIT!
+
+package tipb
+
+import proto "github.com/golang/protobuf/proto"
+import fmt "fmt"
+import math "math"
+
+// Reference imports to suppress errors if they are not otherwise used.
+var _ = proto.Marshal
+var _ = fmt.Errorf
+var _ = math.Inf
+
+// KeyRange is the encoded index key range, low is closed, high is open. (low <= x < high)
+type KeyRange struct {
+	Low              []byte `protobuf:"bytes,1,opt,name=low" json:"low,omitempty"`
+	High             []byte `protobuf:"bytes,2,opt,name=high" json:"high,omitempty"`
+	XXX_unrecognized []byte `json:"-"`
+}
+
+func (m *KeyRange) Reset()                    { *m = KeyRange{} }
+func (m *KeyRange) String() string            { return proto.CompactTextString(m) }
+func (*KeyRange) ProtoMessage()               {}
+func (*KeyRange) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{0} }
+
+func (m *KeyRange) GetLow() []byte {
+	if m != nil {
+		return m.Low
+	}
+	return nil
+}
+
+func (m *KeyRange) GetHigh() []byte {
+	if m != nil {
+		return m.High
+	}
+	return nil
+}
+
+// ByItem type for group by and order by.
+type ByItem struct {
+	Expr             *Expr  `protobuf:"bytes,1,opt,name=expr" json:"expr,omitempty"`
+	Desc             *bool  `protobuf:"varint,2,opt,name=desc" json:"desc,omitempty"`
+	XXX_unrecognized []byte `json:"-"`
+}
+
+func (m *ByItem) Reset()                    { *m = ByItem{} }
+func (m *ByItem) String() string            { return proto.CompactTextString(m) }
+func (*ByItem) ProtoMessage()               {}
+func (*ByItem) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{1} }
+
+func (m *ByItem) GetExpr() *Expr {
+	if m != nil {
+		return m.Expr
+	}
+	return nil
+}
+
+func (m *ByItem) GetDesc() bool {
+	if m != nil && m.Desc != nil {
+		return *m.Desc
+	}
+	return false
+}
+
+// SelectRequest works like a simplified select statement.
+type SelectRequest struct {
+	// transaction start timestamp.
+	StartTs *int64 `protobuf:"varint,1,opt,name=start_ts" json:"start_ts,omitempty"`
+	// If table_info is not null, it represents a table scan, index_info would be null.
+	TableInfo *TableInfo `protobuf:"bytes,2,opt,name=table_info" json:"table_info,omitempty"`
+	// If index_info is not null, it represents an index scan, table_info would be null.
+	IndexInfo *IndexInfo `protobuf:"bytes,3,opt,name=index_info" json:"index_info,omitempty"`
+	// fields to be selected, fields type can be column reference for simple scan.
+	// or aggregation function. If no fields specified, only handle will be returned.
+	Fields []*Expr `protobuf:"bytes,4,rep,name=fields" json:"fields,omitempty"`
+	// disjoint handle ranges to be scanned.
+	Ranges []*KeyRange `protobuf:"bytes,5,rep,name=ranges" json:"ranges,omitempty"`
+	// handle points to be looked up.
+	Points [][]byte `protobuf:"bytes,6,rep,name=points" json:"points,omitempty"`
+	// distinct result.
+	Distinct *bool `protobuf:"varint,7,opt,name=distinct" json:"distinct,omitempty"`
+	// where condition.
+	Where *Expr `protobuf:"bytes,8,opt,name=where" json:"where,omitempty"`
+	// group by clause.
+	GroupBy []*ByItem `protobuf:"bytes,9,rep,name=group_by" json:"group_by,omitempty"`
+	// having clause.
+	Having *Expr `protobuf:"bytes,10,opt,name=having" json:"having,omitempty"`
+	// order by clause.
+	OrderBy []*ByItem `protobuf:"bytes,11,rep,name=order_by" json:"order_by,omitempty"`
+	// limit the result to be returned;
+	Limit            *int64 `protobuf:"varint,12,opt,name=limit" json:"limit,omitempty"`
+	XXX_unrecognized []byte `json:"-"`
+}
+
+func (m *SelectRequest) Reset()                    { *m = SelectRequest{} }
+func (m *SelectRequest) String() string            { return proto.CompactTextString(m) }
+func (*SelectRequest) ProtoMessage()               {}
+func (*SelectRequest) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{2} }
+
+func (m *SelectRequest) GetStartTs() int64 {
+	if m != nil && m.StartTs != nil {
+		return *m.StartTs
+	}
+	return 0
+}
+
+func (m *SelectRequest) GetTableInfo() *TableInfo {
+	if m != nil {
+		return m.TableInfo
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetIndexInfo() *IndexInfo {
+	if m != nil {
+		return m.IndexInfo
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetFields() []*Expr {
+	if m != nil {
+		return m.Fields
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetRanges() []*KeyRange {
+	if m != nil {
+		return m.Ranges
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetPoints() [][]byte {
+	if m != nil {
+		return m.Points
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetDistinct() bool {
+	if m != nil && m.Distinct != nil {
+		return *m.Distinct
+	}
+	return false
+}
+
+func (m *SelectRequest) GetWhere() *Expr {
+	if m != nil {
+		return m.Where
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetGroupBy() []*ByItem {
+	if m != nil {
+		return m.GroupBy
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetHaving() *Expr {
+	if m != nil {
+		return m.Having
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetOrderBy() []*ByItem {
+	if m != nil {
+		return m.OrderBy
+	}
+	return nil
+}
+
+func (m *SelectRequest) GetLimit() int64 {
+	if m != nil && m.Limit != nil {
+		return *m.Limit
+	}
+	return 0
+}
+
+// values are all in text format.
+type Row struct {
+	Handle           []byte `protobuf:"bytes,1,opt,name=handle" json:"handle,omitempty"`
+	Data             []byte `protobuf:"bytes,2,opt,name=data" json:"data,omitempty"`
+	XXX_unrecognized []byte `json:"-"`
+}
+
+func (m *Row) Reset()                    { *m = Row{} }
+func (m *Row) String() string            { return proto.CompactTextString(m) }
+func (*Row) ProtoMessage()               {}
+func (*Row) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{3} }
+
+func (m *Row) GetHandle() []byte {
+	if m != nil {
+		return m.Handle
+	}
+	return nil
+}
+
+func (m *Row) GetData() []byte {
+	if m != nil {
+		return m.Data
+	}
+	return nil
+}
+
+type Error struct {
+	Code             *int32  `protobuf:"varint,1,opt,name=code" json:"code,omitempty"`
+	Msg              *string `protobuf:"bytes,2,opt,name=msg" json:"msg,omitempty"`
+	XXX_unrecognized []byte  `json:"-"`
+}
+
+func (m *Error) Reset()                    { *m = Error{} }
+func (m *Error) String() string            { return proto.CompactTextString(m) }
+func (*Error) ProtoMessage()               {}
+func (*Error) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{4} }
+
+func (m *Error) GetCode() int32 {
+	if m != nil && m.Code != nil {
+		return *m.Code
+	}
+	return 0
+}
+
+func (m *Error) GetMsg() string {
+	if m != nil && m.Msg != nil {
+		return *m.Msg
+	}
+	return ""
+}
+
+// Response for SelectRequest.
+type SelectResponse struct {
+	Error *Error `protobuf:"bytes,1,opt,name=error" json:"error,omitempty"`
+	// Result rows.
+	Rows             []*Row `protobuf:"bytes,2,rep,name=rows" json:"rows,omitempty"`
+	XXX_unrecognized []byte `json:"-"`
+}
+
+func (m *SelectResponse) Reset()                    { *m = SelectResponse{} }
+func (m *SelectResponse) String() string            { return proto.CompactTextString(m) }
+func (*SelectResponse) ProtoMessage()               {}
+func (*SelectResponse) Descriptor() ([]byte, []int) { return fileDescriptor2, []int{5} }
+
+func (m *SelectResponse) GetError() *Error {
+	if m != nil {
+		return m.Error
+	}
+	return nil
+}
+
+func (m *SelectResponse) GetRows() []*Row {
+	if m != nil {
+		return m.Rows
+	}
+	return nil
+}
+
+func init() {
+	proto.RegisterType((*KeyRange)(nil), "tipb.KeyRange")
+	proto.RegisterType((*ByItem)(nil), "tipb.ByItem")
+	proto.RegisterType((*SelectRequest)(nil), "tipb.SelectRequest")
+	proto.RegisterType((*Row)(nil), "tipb.Row")
+	proto.RegisterType((*Error)(nil), "tipb.Error")
+	proto.RegisterType((*SelectResponse)(nil), "tipb.SelectResponse")
+}
+
+var fileDescriptor2 = []byte{
+	// 404 bytes of a gzipped FileDescriptorProto
+	0x1f, 0x8b, 0x08, 0x00, 0x00, 0x09, 0x6e, 0x88, 0x02, 0xff, 0x6c, 0x51, 0x5d, 0x6b, 0xdb, 0x30,
+	0x14, 0x25, 0xf5, 0xc7, 0x9c, 0x6b, 0x37, 0x2b, 0x86, 0x31, 0x35, 0x0f, 0xa5, 0xb8, 0x0c, 0xf6,
+	0x14, 0x46, 0x7f, 0x42, 0x21, 0x0f, 0x61, 0x2f, 0x23, 0xdb, 0x7b, 0x50, 0xac, 0x5b, 0x5b, 0x60,
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+	0xe3, 0xfa, 0x1c, 0x1d, 0xa8, 0x2c, 0x0e, 0xd8, 0xba, 0xcd, 0x64, 0xb4, 0xd3, 0x75, 0xea, 0xe4,
+	0x74, 0x5c, 0x5f, 0xe1, 0xf3, 0x64, 0xd0, 0x5a, 0xa9, 0x55, 0xc4, 0xd7, 0x95, 0x6d, 0x7b, 0x1c,
+	0x79, 0xfc, 0x6a, 0x3e, 0x40, 0xf1, 0x19, 0xcf, 0x7b, 0xae, 0x3a, 0xac, 0x4b, 0x48, 0x06, 0x7d,
+	0x62, 0x8b, 0xdb, 0xc5, 0xc7, 0xaa, 0xae, 0x20, 0xed, 0x65, 0xd7, 0xb3, 0x0b, 0xfa, 0x6a, 0x3e,
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+	0x97, 0xcd, 0xd6, 0x23, 0xe4, 0x10, 0x68, 0xdb, 0xe0, 0x28, 0x9a, 0x9f, 0x17, 0x70, 0xf9, 0x35,
+	0xe4, 0xd9, 0xe3, 0xf7, 0x27, 0xb4, 0xae, 0xbe, 0x82, 0xc2, 0x3a, 0x6e, 0xdc, 0xc1, 0xd9, 0xe0,
+	0x4e, 0xea, 0x3b, 0x00, 0xc7, 0x8f, 0x03, 0x1e, 0xa4, 0x7a, 0xd4, 0xc1, 0x57, 0xde, 0xbf, 0x8d,
+	0x17, 0xbf, 0x11, 0xbe, 0xf3, 0x30, 0x89, 0xa4, 0x12, 0xf8, 0x1c, 0x45, 0xc9, 0xbf, 0xa2, 0x1d,
+	0xe1, 0x41, 0xb4, 0x86, 0xfc, 0x51, 0xe2, 0x20, 0x2c, 0x4b, 0x6f, 0x93, 0xff, 0x72, 0xdd, 0x40,
+	0x6e, 0xa8, 0x9f, 0x65, 0x59, 0xe0, 0x56, 0x91, 0xfb, 0x53, 0x7b, 0x05, 0xf9, 0xa4, 0xa5, 0xf2,
+	0xa9, 0x72, 0xcf, 0x57, 0x94, 0x53, 0x48, 0xeb, 0xa4, 0x6a, 0x1d, 0x7b, 0x43, 0x5d, 0xea, 0x6b,
+	0xc8, 0x4e, 0x3d, 0x1a, 0x64, 0xc5, 0x8b, 0xd2, 0x37, 0x50, 0x74, 0x46, 0x3f, 0x4d, 0x87, 0xe3,
+	0x99, 0x2d, 0xc3, 0xf9, 0x2a, 0xb2, 0xf3, 0x73, 0xf9, 0x60, 0x3d, 0xff, 0x21, 0x55, 0xc7, 0xe0,
+	0x35, 0xaf, 0x36, 0x02, 0x0d, 0x79, 0xcb, 0x57, 0xbc, 0x97, 0x90, 0x0d, 0x72, 0x94, 0x8e, 0x55,
+	0xf4, 0x5a, 0xcd, 0x1d, 0x24, 0x7b, 0x7d, 0xa2, 0xb8, 0x3d, 0x57, 0x62, 0xc0, 0xbf, 0x43, 0x09,
+	0xee, 0xf8, 0x3c, 0x54, 0x03, 0xd9, 0xd6, 0x18, 0x1d, 0xd6, 0x68, 0xb5, 0x88, 0xa2, 0x8c, 0xa6,
+	0x1d, 0x6d, 0x17, 0x34, 0xcb, 0x66, 0x0b, 0xab, 0xdf, 0xcb, 0xd8, 0x49, 0x2b, 0x8b, 0x3e, 0x65,
+	0x86, 0xe4, 0x9a, 0x57, 0x2d, 0xe7, 0x90, 0xe1, 0xd0, 0x7b, 0x48, 0x8d, 0x3e, 0x59, 0xef, 0xa5,
+	0x84, 0xcb, 0x48, 0xf9, 0x20, 0x0f, 0xd7, 0xf0, 0xae, 0xd5, 0xe3, 0x66, 0xf2, 0xe5, 0x5a, 0x3e,
+	0x79, 0x5c, 0x1c, 0x03, 0xf9, 0x65, 0xf1, 0x2b, 0x00, 0x00, 0xff, 0xff, 0x1f, 0xa1, 0xaf, 0xe2,
+	0x8a, 0x02, 0x00, 0x00,
+}
diff --git a/xapi/tipb/select.proto b/xapi/tipb/select.proto
new file mode 100644
index 0000000000..8f623fe9a4
--- /dev/null
+++ b/xapi/tipb/select.proto
@@ -0,0 +1,80 @@
+syntax = "proto2";
+
+package tipb;
+
+option java_multiple_files = true;
+option java_package = "com.pingcap.tidb.tipb";
+
+import "expression.proto";
+import "schema.proto";
+
+// KeyRange is the encoded index key range, low is closed, high is open. (low <= x < high)
+message KeyRange {
+	optional bytes low = 1;
+	optional bytes high = 2;
+}
+
+// ByItem type for group by and order by.
+message ByItem {
+	optional Expr expr = 1;
+	optional bool desc = 2;
+}
+
+// SelectRequest works like a simplified select statement.
+message SelectRequest {
+	// transaction start timestamp.
+	optional int64 start_ts = 1;
+
+	// If table_info is not null, it represents a table scan, index_info would be null.
+	optional TableInfo table_info = 2;
+
+	// If index_info is not null, it represents an index scan, table_info would be null.
+	optional IndexInfo index_info = 3;
+
+	// fields to be selected, fields type can be column reference for simple scan.
+	// or aggregation function. If no fields specified, only handle will be returned.
+	repeated Expr fields = 4;
+
+	// disjoint handle ranges to be scanned.
+	repeated KeyRange ranges = 5;
+
+	// handle points to be looked up.
+	repeated bytes points = 6;
+
+	// distinct result.
+	optional bool distinct = 7;
+
+	// where condition.
+	optional Expr where = 8;
+
+	// group by clause.
+	repeated ByItem group_by = 9;
+
+	// having clause.
+	optional Expr having = 10;
+
+	// order by clause.
+	repeated ByItem order_by = 11;
+
+	// limit the result to be returned;
+	optional int64 limit = 12;
+}
+
+// values are all in text format.
+message Row {
+	optional bytes handle = 1;
+	optional bytes data = 2;
+}
+
+message Error {
+	optional int32 code = 1;
+	optional string msg = 2;
+}
+
+// Response for SelectRequest.
+message SelectResponse {
+	optional Error error = 1;
+
+	// Result rows.
+	repeated Row rows = 2;
+}