builtin_convert_charset.go

// Copyright 2021 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,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package expression

import (
	"fmt"

	"github.com/pingcap/tidb/parser/ast"
	"github.com/pingcap/tidb/parser/charset"
	"github.com/pingcap/tidb/parser/model"
	"github.com/pingcap/tidb/sessionctx"
	"github.com/pingcap/tidb/types"
	"github.com/pingcap/tidb/util/chunk"
	"github.com/pingcap/tipb/go-tipb"
)

// InternalFuncToBinary accepts a string and returns another string encoded in a given charset.
const InternalFuncToBinary = "to_binary"

type tidbConvertCharsetFunctionClass struct {
	baseFunctionClass
}

func (c *tidbConvertCharsetFunctionClass) getFunction(ctx sessionctx.Context, args []Expression) (builtinFunc, error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, c.verifyArgs(args)
	}
	argTp := args[0].GetType().EvalType()
	var sig builtinFunc
	switch argTp {
	case types.ETString:
		bf, err := newBaseBuiltinFuncWithTp(ctx, c.funcName, args, types.ETString, types.ETString)
		if err != nil {
			return nil, err
		}
		sig = &builtinInternalToBinarySig{bf}
		sig.setPbCode(tipb.ScalarFuncSig_ToBinary)
	default:
		return nil, fmt.Errorf("unexpected argTp: %d", argTp)
	}
	return sig, nil
}

var _ builtinFunc = &builtinInternalToBinarySig{}

type builtinInternalToBinarySig struct {
	baseBuiltinFunc
}

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

func (b *builtinInternalToBinarySig) evalString(row chunk.Row) (res string, isNull bool, err error) {
	val, isNull, err := b.args[0].EvalString(b.ctx, row)
	if isNull || err != nil {
		return res, isNull, err
	}
	tp := b.args[0].GetType()
	enc := charset.NewEncoding(tp.Charset)
	res, err = enc.EncodeString(val)
	return res, false, err
}

func (b *builtinInternalToBinarySig) vectorized() bool {
	return true
}

func (b *builtinInternalToBinarySig) vecEvalString(input *chunk.Chunk, result *chunk.Column) error {
	n := input.NumRows()
	buf, err := b.bufAllocator.get()
	if err != nil {
		return err
	}
	defer b.bufAllocator.put(buf)
	if err := b.args[0].VecEvalString(b.ctx, input, buf); err != nil {
		return err
	}
	enc := charset.NewEncoding(b.args[0].GetType().Charset)
	result.ReserveString(n)
	var encodedBuf []byte
	for i := 0; i < n; i++ {
		if buf.IsNull(i) {
			result.AppendNull()
			continue
		}
		strBytes, err := enc.Encode(encodedBuf, buf.GetBytes(i))
		if err != nil {
			return err
		}
		result.AppendBytes(strBytes)
	}
	return nil
}

// toBinaryMap contains the builtin functions which arguments need to be converted to the correct charset.
var toBinaryMap = map[string]struct{}{
	ast.Hex: {}, ast.Length: {}, ast.OctetLength: {}, ast.ASCII: {},
	ast.ToBase64: {}, ast.AesDecrypt: {}, ast.Decode: {}, ast.Encode: {},
	ast.PasswordFunc: {}, ast.MD5: {}, ast.SHA: {}, ast.SHA1: {},
	ast.SHA2: {}, ast.Compress: {},
}

// WrapWithToBinary wraps `expr` with to_binary sig.
func WrapWithToBinary(ctx sessionctx.Context, expr Expression, funcName string) Expression {
	exprTp := expr.GetType()
	if _, err := charset.GetDefaultCollationLegacy(exprTp.Charset); err != nil {
		if _, ok := toBinaryMap[funcName]; ok {
			fc := funcs[InternalFuncToBinary]
			sig, err := fc.getFunction(ctx, []Expression{expr})
			if err != nil {
				return expr
			}
			sf := &ScalarFunction{
				FuncName: model.NewCIStr(InternalFuncToBinary),
				RetType:  exprTp,
				Function: sig,
			}
			return FoldConstant(sf)
		}
	}
	return expr
}