builtin_cast.go

// Copyright 2017 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.

// We implement 6 CastAsXXFunctionClass for `cast` built-in functions.
// XX means the return type of the `cast` built-in functions.
// XX contains the following 6 types:
// Int, Decimal, Real, String.

// We implement 6 CastYYAsXXSig built-in function signatures for every CastAsXXFunctionClass.
// builtinCastXXAsYYSig takes a argument of type XX and returns a value of type YY.

package expression

import (
	"fmt"

	"github.com/secretflow/scql/pkg/parser/ast"
	"github.com/secretflow/scql/pkg/parser/charset"
	"github.com/secretflow/scql/pkg/parser/model"
	"github.com/secretflow/scql/pkg/parser/mysql"
	"github.com/secretflow/scql/pkg/parser/terror"
	"github.com/secretflow/scql/pkg/sessionctx"
	"github.com/secretflow/scql/pkg/types"
	"github.com/secretflow/scql/pkg/util/chunk"
)

var (
	_ functionClass = &castAsIntFunctionClass{}
	_ functionClass = &castAsRealFunctionClass{}
	_ functionClass = &castAsStringFunctionClass{}
	_ functionClass = &castAsDecimalFunctionClass{}
	_ functionClass = &castAsTimeFunctionClass{}
)

var (
	_ builtinFunc = &builtinCastIntAsIntSig{}
	_ builtinFunc = &builtinCastIntAsRealSig{}
	_ builtinFunc = &builtinCastIntAsStringSig{}
	_ builtinFunc = &builtinCastIntAsDecimalSig{}
	_ builtinFunc = &builtinCastIntAsTimeSig{}

	_ builtinFunc = &builtinCastRealAsIntSig{}
	_ builtinFunc = &builtinCastRealAsRealSig{}
	_ builtinFunc = &builtinCastRealAsStringSig{}
	_ builtinFunc = &builtinCastRealAsDecimalSig{}
	_ builtinFunc = &builtinCastRealAsTimeSig{}

	_ builtinFunc = &builtinCastDecimalAsIntSig{}
	_ builtinFunc = &builtinCastDecimalAsRealSig{}
	_ builtinFunc = &builtinCastDecimalAsStringSig{}
	_ builtinFunc = &builtinCastDecimalAsDecimalSig{}
	_ builtinFunc = &builtinCastDecimalAsTimeSig{}

	_ builtinFunc = &builtinCastStringAsIntSig{}
	_ builtinFunc = &builtinCastStringAsRealSig{}
	_ builtinFunc = &builtinCastStringAsStringSig{}
	_ builtinFunc = &builtinCastStringAsDecimalSig{}
	_ builtinFunc = &builtinCastStringAsTimeSig{}

	_ builtinFunc = &builtinCastTimeAsIntSig{}
	_ builtinFunc = &builtinCastTimeAsRealSig{}
	_ builtinFunc = &builtinCastTimeAsStringSig{}
	_ builtinFunc = &builtinCastTimeAsDecimalSig{}
	_ builtinFunc = &builtinCastTimeAsTimeSig{}
)

type castAsIntFunctionClass struct {
	baseFunctionClass

	tp *types.FieldType
}

func (c *castAsIntFunctionClass) getFunction(ctx sessionctx.Context, args []Expression) (sig builtinFunc, err error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, err
	}
	bf := newBaseBuiltinCastFunc(newBaseBuiltinFunc(ctx, args), ctx.Value(inUnionCastContext) != nil)
	bf.tp = c.tp
	if args[0].GetType().Hybrid() || IsBinaryLiteral(args[0]) {
		sig = &builtinCastIntAsIntSig{bf}
		return sig, nil
	}
	argTp := args[0].GetType().EvalType()
	switch argTp {
	case types.ETInt:
		sig = &builtinCastIntAsIntSig{bf}
	case types.ETReal:
		sig = &builtinCastRealAsIntSig{bf}
	case types.ETDecimal:
		sig = &builtinCastDecimalAsIntSig{bf}
	case types.ETString:
		sig = &builtinCastStringAsIntSig{bf}
	default:
		panic("unsupported types.EvalType in castAsIntFunctionClass")
	}
	return sig, nil
}

type castAsRealFunctionClass struct {
	baseFunctionClass

	tp *types.FieldType
}

func (c *castAsRealFunctionClass) getFunction(ctx sessionctx.Context, args []Expression) (sig builtinFunc, err error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, err
	}
	bf := newBaseBuiltinCastFunc(newBaseBuiltinFunc(ctx, args), ctx.Value(inUnionCastContext) != nil)
	bf.tp = c.tp
	if IsBinaryLiteral(args[0]) {
		sig = &builtinCastRealAsRealSig{bf}
		return sig, nil
	}
	var argTp types.EvalType
	if args[0].GetType().Hybrid() {
		argTp = types.ETInt
	} else {
		argTp = args[0].GetType().EvalType()
	}
	switch argTp {
	case types.ETInt:
		sig = &builtinCastIntAsRealSig{bf}
	case types.ETReal:
		sig = &builtinCastRealAsRealSig{bf}
	case types.ETDecimal:
		sig = &builtinCastDecimalAsRealSig{bf}
	case types.ETString:
		sig = &builtinCastStringAsRealSig{bf}
	default:
		panic("unsupported types.EvalType in castAsRealFunctionClass")
	}
	return sig, nil
}

type castAsDecimalFunctionClass struct {
	baseFunctionClass

	tp *types.FieldType
}

func (c *castAsDecimalFunctionClass) getFunction(ctx sessionctx.Context, args []Expression) (sig builtinFunc, err error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, err
	}
	bf := newBaseBuiltinCastFunc(newBaseBuiltinFunc(ctx, args), ctx.Value(inUnionCastContext) != nil)
	bf.tp = c.tp
	if IsBinaryLiteral(args[0]) {
		sig = &builtinCastDecimalAsDecimalSig{bf}
		return sig, nil
	}
	var argTp types.EvalType
	if args[0].GetType().Hybrid() {
		argTp = types.ETInt
	} else {
		argTp = args[0].GetType().EvalType()
	}
	switch argTp {
	case types.ETInt:
		sig = &builtinCastIntAsDecimalSig{bf}
	case types.ETReal:
		sig = &builtinCastRealAsDecimalSig{bf}
	case types.ETDecimal:
		sig = &builtinCastDecimalAsDecimalSig{bf}
	case types.ETString:
		sig = &builtinCastStringAsDecimalSig{bf}
	default:
		panic("unsupported types.EvalType in castAsDecimalFunctionClass")
	}
	return sig, nil
}

type castAsStringFunctionClass struct {
	baseFunctionClass

	tp *types.FieldType
}

func (c *castAsStringFunctionClass) getFunction(ctx sessionctx.Context, args []Expression) (sig builtinFunc, err error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, err
	}
	bf := newBaseBuiltinFunc(ctx, args)
	bf.tp = c.tp
	if args[0].GetType().Hybrid() || IsBinaryLiteral(args[0]) {
		sig = &builtinCastStringAsStringSig{bf}
		return sig, nil
	}
	argTp := args[0].GetType().EvalType()
	switch argTp {
	case types.ETInt:
		sig = &builtinCastIntAsStringSig{bf}
	case types.ETReal:
		sig = &builtinCastRealAsStringSig{bf}
	case types.ETDecimal:
		sig = &builtinCastDecimalAsStringSig{bf}
	case types.ETString:
		sig = &builtinCastStringAsStringSig{bf}
	default:
		panic("unsupported types.EvalType in castAsStringFunctionClass")
	}
	return sig, nil
}

type builtinCastIntAsIntSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastIntAsIntSig) Clone() builtinFunc {
	newSig := &builtinCastIntAsIntSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastIntAsRealSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastIntAsRealSig) Clone() builtinFunc {
	newSig := &builtinCastIntAsRealSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastIntAsDecimalSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastIntAsDecimalSig) Clone() builtinFunc {
	newSig := &builtinCastIntAsDecimalSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastIntAsStringSig struct {
	baseBuiltinFunc
}

func (b *builtinCastIntAsStringSig) Clone() builtinFunc {
	newSig := &builtinCastIntAsStringSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

type builtinCastRealAsRealSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastRealAsRealSig) Clone() builtinFunc {
	newSig := &builtinCastRealAsRealSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastRealAsIntSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastRealAsIntSig) Clone() builtinFunc {
	newSig := &builtinCastRealAsIntSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastRealAsDecimalSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastRealAsDecimalSig) Clone() builtinFunc {
	newSig := &builtinCastRealAsDecimalSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastRealAsStringSig struct {
	baseBuiltinFunc
}

func (b *builtinCastRealAsStringSig) Clone() builtinFunc {
	newSig := &builtinCastRealAsStringSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

type builtinCastDecimalAsDecimalSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastDecimalAsDecimalSig) Clone() builtinFunc {
	newSig := &builtinCastDecimalAsDecimalSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastDecimalAsIntSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastDecimalAsIntSig) Clone() builtinFunc {
	newSig := &builtinCastDecimalAsIntSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastDecimalAsStringSig struct {
	baseBuiltinFunc
}

func (b *builtinCastDecimalAsStringSig) Clone() builtinFunc {
	newSig := &builtinCastDecimalAsStringSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

type builtinCastDecimalAsRealSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastDecimalAsRealSig) Clone() builtinFunc {
	newSig := &builtinCastDecimalAsRealSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastStringAsStringSig struct {
	baseBuiltinFunc
}

func (b *builtinCastStringAsStringSig) Clone() builtinFunc {
	newSig := &builtinCastStringAsStringSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

type builtinCastStringAsIntSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastStringAsIntSig) Clone() builtinFunc {
	newSig := &builtinCastStringAsIntSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastStringAsRealSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastStringAsRealSig) Clone() builtinFunc {
	newSig := &builtinCastStringAsRealSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

type builtinCastStringAsDecimalSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastStringAsDecimalSig) Clone() builtinFunc {
	newSig := &builtinCastStringAsDecimalSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

// inCastContext is session key type that indicates whether executing
// in special cast context that negative unsigned num will be zero.
type inCastContext int

func (i inCastContext) String() string {
	return "__cast_ctx"
}

// inUnionCastContext is session key value that indicates whether executing in
// union cast context.
// @see BuildCastFunction4Union
const inUnionCastContext inCastContext = 0

// hasSpecialCast checks if this expr has its own special cast function.
// for example(#9713): when doing arithmetic using results of function DayName,
// "Monday" should be regarded as 0, "Tuesday" should be regarded as 1 and so on.
func hasSpecialCast(ctx sessionctx.Context, expr Expression, tp *types.FieldType) bool {
	switch f := expr.(type) {
	case *ScalarFunction:
		switch f.FuncName.L {
		case ast.DayName:
			switch tp.EvalType() {
			case types.ETInt, types.ETReal:
				return true
			}
		}
	}
	return false
}

// BuildCastFunction4Union build a implicitly CAST ScalarFunction from the Union
// Expression.
func BuildCastFunction4Union(ctx sessionctx.Context, expr Expression, tp *types.FieldType) (res Expression) {
	ctx.SetValue(inUnionCastContext, struct{}{})
	defer func() {
		ctx.SetValue(inUnionCastContext, nil)
	}()
	return BuildCastFunction(ctx, expr, tp)
}

// BuildCastFunction builds a CAST ScalarFunction from the Expression.
func BuildCastFunction(ctx sessionctx.Context, expr Expression, tp *types.FieldType) (res Expression) {
	if hasSpecialCast(ctx, expr, tp) {
		return expr
	}

	var fc functionClass
	switch tp.EvalType() {
	case types.ETInt:
		fc = &castAsIntFunctionClass{baseFunctionClass{ast.Cast, 1, 1}, tp}
	case types.ETDecimal:
		fc = &castAsDecimalFunctionClass{baseFunctionClass{ast.Cast, 1, 1}, tp}
	case types.ETReal:
		fc = &castAsRealFunctionClass{baseFunctionClass{ast.Cast, 1, 1}, tp}
	case types.ETString:
		fc = &castAsStringFunctionClass{baseFunctionClass{ast.Cast, 1, 1}, tp}
	case types.ETDatetime, types.ETTimestamp:
		fc = &castAsTimeFunctionClass{baseFunctionClass{ast.Cast, 1, 1}, tp}
	default:
		terror.Log(fmt.Errorf("unsupported data type in cast: %+v", tp.EvalType()))
		return
	}
	f, err := fc.getFunction(ctx, []Expression{expr})
	terror.Log(err)
	res = &ScalarFunction{
		FuncName: model.NewCIStr(ast.Cast),
		RetType:  tp,
		Function: f,
	}
	return res
}

// 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().EvalType() == types.ETInt {
		return expr
	}
	tp := types.NewFieldType(mysql.TypeLonglong)
	tp.Flen, tp.Decimal = expr.GetType().Flen, 0
	types.SetBinChsClnFlag(tp)
	tp.Flag |= expr.GetType().Flag & mysql.UnsignedFlag
	return BuildCastFunction(ctx, expr, tp)
}

// WrapWithCastAsReal wraps `expr` with `cast` if the return type of expr is not
// type real, otherwise, returns `expr` directly.
func WrapWithCastAsReal(ctx sessionctx.Context, expr Expression) Expression {
	if expr.GetType().EvalType() == types.ETReal {
		return expr
	}
	tp := types.NewFieldType(mysql.TypeDouble)
	tp.Flen, tp.Decimal = mysql.MaxRealWidth, types.UnspecifiedLength
	types.SetBinChsClnFlag(tp)
	tp.Flag |= expr.GetType().Flag & mysql.UnsignedFlag
	return BuildCastFunction(ctx, expr, tp)
}

// WrapWithCastAsDecimal wraps `expr` with `cast` if the return type of expr is
// not type decimal, otherwise, returns `expr` directly.
func WrapWithCastAsDecimal(ctx sessionctx.Context, expr Expression) Expression {
	if expr.GetType().EvalType() == types.ETDecimal {
		return expr
	}
	tp := types.NewFieldType(mysql.TypeNewDecimal)
	tp.Flen, tp.Decimal = expr.GetType().Flen, expr.GetType().Decimal
	if expr.GetType().EvalType() == types.ETInt {
		tp.Flen = mysql.MaxIntWidth
	}
	types.SetBinChsClnFlag(tp)
	tp.Flag |= expr.GetType().Flag & mysql.UnsignedFlag
	return BuildCastFunction(ctx, expr, tp)
}

// WrapWithCastAsTime wraps `expr` with `cast` if the return type of expr is not
// same as type of the specified `tp` , otherwise, returns `expr` directly.
func WrapWithCastAsTime(ctx sessionctx.Context, expr Expression, tp *types.FieldType) Expression {
	exprTp := expr.GetType().Tp
	if tp.Tp == exprTp {
		return expr
	} else if (exprTp == mysql.TypeDate || exprTp == mysql.TypeTimestamp) && tp.Tp == mysql.TypeDatetime {
		return expr
	}
	switch x := expr.GetType(); x.Tp {
	case mysql.TypeDatetime, mysql.TypeTimestamp, mysql.TypeDate, mysql.TypeDuration:
		tp.Decimal = x.Decimal
	default:
		tp.Decimal = int(types.MaxFsp)
	}
	switch tp.Tp {
	case mysql.TypeDate:
		tp.Flen = mysql.MaxDateWidth
	case mysql.TypeDatetime, mysql.TypeTimestamp:
		tp.Flen = mysql.MaxDatetimeWidthNoFsp
		if tp.Decimal > 0 {
			tp.Flen = tp.Flen + 1 + tp.Decimal
		}
	}
	types.SetBinChsClnFlag(tp)
	return BuildCastFunction(ctx, expr, tp)
}

// WrapWithCastAsString wraps `expr` with `cast` if the return type of expr is
// not type string, otherwise, returns `expr` directly.
func WrapWithCastAsString(ctx sessionctx.Context, expr Expression) Expression {
	exprTp := expr.GetType()
	if exprTp.EvalType() == types.ETString {
		return expr
	}
	argLen := exprTp.Flen
	// If expr is decimal, we should take the decimal point and negative sign
	// into consideration, so we set `expr.GetType().Flen + 2` as the `argLen`.
	// Since the length of float and double is not accurate, we do not handle
	// them.
	if exprTp.Tp == mysql.TypeNewDecimal && argLen != int(types.UnspecifiedFsp) {
		argLen += 2
	}
	if exprTp.EvalType() == types.ETInt {
		argLen = mysql.MaxIntWidth
	}
	tp := types.NewFieldType(mysql.TypeVarString)
	tp.Charset, tp.Collate = charset.GetDefaultCharsetAndCollate()
	tp.Flen, tp.Decimal = argLen, types.UnspecifiedLength
	return BuildCastFunction(ctx, expr, tp)
}

// WrapWithCastAsDuration wraps `expr` with `cast` if the return type of expr is
// not type duration, otherwise, returns `expr` directly.
func WrapWithCastAsDuration(ctx sessionctx.Context, expr Expression) Expression {
	if expr.GetType().Tp == mysql.TypeDuration {
		return expr
	}
	tp := types.NewFieldType(mysql.TypeDuration)
	switch x := expr.GetType(); x.Tp {
	case mysql.TypeDatetime, mysql.TypeTimestamp, mysql.TypeDate:
		tp.Decimal = x.Decimal
	default:
		tp.Decimal = int(types.MaxFsp)
	}
	tp.Flen = mysql.MaxDurationWidthNoFsp
	if tp.Decimal > 0 {
		tp.Flen = tp.Flen + 1 + tp.Decimal
	}
	return BuildCastFunction(ctx, expr, tp)
}

// WrapWithCastAsJSON wraps `expr` with `cast` if the return type of expr is not
// type json, otherwise, returns `expr` directly.
func WrapWithCastAsJSON(ctx sessionctx.Context, expr Expression) Expression {
	if expr.GetType().Tp == mysql.TypeJSON && !mysql.HasParseToJSONFlag(expr.GetType().Flag) {
		return expr
	}
	tp := &types.FieldType{
		Tp:      mysql.TypeJSON,
		Flen:    12582912, // FIXME: Here the Flen is not trusted.
		Decimal: 0,
		Charset: mysql.DefaultCharset,
		Collate: mysql.DefaultCollationName,
		Flag:    mysql.BinaryFlag,
	}
	return BuildCastFunction(ctx, expr, tp)
}

type castAsTimeFunctionClass struct {
	baseFunctionClass

	tp *types.FieldType
}

func (c *castAsTimeFunctionClass) getFunction(ctx sessionctx.Context, args []Expression) (sig builtinFunc, err error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, err
	}
	bf := newBaseBuiltinFunc(ctx, args)
	bf.tp = c.tp
	argTp := args[0].GetType().EvalType()
	switch argTp {
	case types.ETInt:
		sig = &builtinCastIntAsTimeSig{bf}
	case types.ETReal:
		sig = &builtinCastRealAsTimeSig{bf}
	case types.ETDecimal:
		sig = &builtinCastDecimalAsTimeSig{bf}
	case types.ETDatetime, types.ETTimestamp:
		sig = &builtinCastTimeAsTimeSig{bf}
	case types.ETString:
		sig = &builtinCastStringAsTimeSig{bf}
	default:
		panic("unsupported types.EvalType in castAsTimeFunctionClass")
	}
	return sig, nil
}

type builtinCastIntAsTimeSig struct {
	baseBuiltinFunc
}

func (b *builtinCastIntAsTimeSig) Clone() builtinFunc {
	newSig := &builtinCastIntAsTimeSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

func (b *builtinCastIntAsTimeSig) evalTime(row chunk.Row) (res types.Time, isNull bool, err error) {
	return res, false, nil
}

type builtinCastRealAsTimeSig struct {
	baseBuiltinFunc
}

func (b *builtinCastRealAsTimeSig) Clone() builtinFunc {
	newSig := &builtinCastRealAsTimeSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

func (b *builtinCastRealAsTimeSig) evalTime(row chunk.Row) (types.Time, bool, error) {
	return types.Time{}, false, nil
}

type builtinCastDecimalAsTimeSig struct {
	baseBuiltinFunc
}

func (b *builtinCastDecimalAsTimeSig) Clone() builtinFunc {
	newSig := &builtinCastDecimalAsTimeSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

func (b *builtinCastDecimalAsTimeSig) evalTime(row chunk.Row) (res types.Time, isNull bool, err error) {
	return types.Time{}, false, nil
}

type builtinCastTimeAsTimeSig struct {
	baseBuiltinFunc
}

func (b *builtinCastTimeAsTimeSig) Clone() builtinFunc {
	newSig := &builtinCastTimeAsTimeSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

func (b *builtinCastTimeAsTimeSig) evalTime(row chunk.Row) (res types.Time, isNull bool, err error) {
	res, isNull, err = b.args[0].EvalTime(b.ctx, row)
	if isNull || err != nil {
		return res, isNull, err
	}

	sc := b.ctx.GetSessionVars().StmtCtx
	if res, err = res.Convert(sc, b.tp.Tp); err != nil {
		return types.ZeroTime, true, handleInvalidTimeError(b.ctx, err)
	}
	res, err = res.RoundFrac(sc, int8(b.tp.Decimal))
	if b.tp.Tp == mysql.TypeDate {
		// Truncate hh:mm:ss part if the type is Date.
		res.SetCoreTime(types.FromDate(res.Year(), res.Month(), res.Day(), 0, 0, 0, 0))
		res.SetType(b.tp.Tp)
	}
	return res, false, err
}

type builtinCastStringAsTimeSig struct {
	baseBuiltinFunc
}

func (b *builtinCastStringAsTimeSig) Clone() builtinFunc {
	newSig := &builtinCastStringAsTimeSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

func (b *builtinCastStringAsTimeSig) evalTime(row chunk.Row) (res types.Time, isNull bool, err error) {
	val, isNull, err := b.args[0].EvalString(b.ctx, row)
	if isNull || err != nil {
		return res, isNull, err
	}
	sc := b.ctx.GetSessionVars().StmtCtx
	res, err = types.ParseTime(sc, val, b.tp.Tp, int8(b.tp.Decimal))
	if err != nil {
		return types.ZeroTime, true, handleInvalidTimeError(b.ctx, err)
	}
	if b.tp.Tp == mysql.TypeDate {
		// Truncate hh:mm:ss part if the type is Date.
		res.SetCoreTime(types.FromDate(res.Year(), res.Month(), res.Day(), 0, 0, 0, 0))
	}
	return res, false, nil
}

type builtinCastTimeAsIntSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastTimeAsIntSig) Clone() builtinFunc {
	newSig := &builtinCastTimeAsIntSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

func (b *builtinCastTimeAsIntSig) evalInt(row chunk.Row) (res int64, isNull bool, err error) {
	return 0, false, nil
}

type builtinCastTimeAsRealSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastTimeAsRealSig) Clone() builtinFunc {
	newSig := &builtinCastTimeAsRealSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

func (b *builtinCastTimeAsRealSig) evalReal(row chunk.Row) (res float64, isNull bool, err error) {
	return 0.0, false, nil
}

type builtinCastTimeAsDecimalSig struct {
	baseBuiltinCastFunc
}

func (b *builtinCastTimeAsDecimalSig) Clone() builtinFunc {
	newSig := &builtinCastTimeAsDecimalSig{}
	newSig.cloneFrom(&b.baseBuiltinCastFunc)
	return newSig
}

func (b *builtinCastTimeAsDecimalSig) evalDecimal(row chunk.Row) (res *types.MyDecimal, isNull bool, err error) {
	return nil, false, nil
}

type builtinCastTimeAsStringSig struct {
	baseBuiltinFunc
}

func (b *builtinCastTimeAsStringSig) Clone() builtinFunc {
	newSig := &builtinCastTimeAsStringSig{}
	newSig.cloneFrom(&b.baseBuiltinFunc)
	return newSig
}

func (b *builtinCastTimeAsStringSig) evalString(row chunk.Row) (res string, isNull bool, err error) {
	return "", false, nil
}