func isTokenIdentifier(s string, buf *bytes.Buffer) int {
	buf.Reset()
	buf.Grow(len(s))
	data := buf.Bytes()[:len(s)]
	for i := 0; i < len(s); i++ {
		if s[i] >= 'a' && s[i] <= 'z' {
			data[i] = s[i] + 'A' - 'a'
		} else {
			data[i] = s[i]
		}
	}
	tok := tokenMap[hack.String(data)]
	return tok
}

// dispatch handles client request based on command which is the first byte of the data.
// It also gets a token from server which is used to limit the concurrently handling clients.
// The most frequently used command is ComQuery.
func (cc *clientConn) dispatch(data []byte) error {
	cmd := data[0]
	data = data[1:]
	cc.lastCmd = hack.String(data)

	token := cc.server.getToken()

	startTS := time.Now()
	defer func() {
		cc.server.releaseToken(token)
		log.Debugf("[TIME_CMD] %v %d", time.Since(startTS), cmd)
	}()

	switch cmd {
	case mysql.ComSleep:
		// TODO: According to mysql document, this command is supposed to be used only internally.
		// So it's just a temp fix, not sure if it's done right.
		// Investigate this command and write test case later.
		return nil
	case mysql.ComQuit:
		return io.EOF
	case mysql.ComQuery: // Most frequently used command.
		// For issue 1989
		// Input payload may end with byte '\0', we didn't find related mysql document about it, but mysql
		// implementation accept that case. So trim the last '\0' here as if the payload an EOF string.
		// See http://dev.mysql.com/doc/internals/en/com-query.html
		if data[len(data)-1] == 0 {
			data = data[:len(data)-1]
		}
		return cc.handleQuery(hack.String(data))
	case mysql.ComPing:
		return cc.writeOK()
	case mysql.ComInitDB:
		log.Debug("init db", hack.String(data))
		if err := cc.useDB(hack.String(data)); err != nil {
			return errors.Trace(err)
		}
		return cc.writeOK()
	case mysql.ComFieldList:
		return cc.handleFieldList(hack.String(data))
	case mysql.ComStmtPrepare:
		return cc.handleStmtPrepare(hack.String(data))
	case mysql.ComStmtExecute:
		return cc.handleStmtExecute(data)
	case mysql.ComStmtClose:
		return cc.handleStmtClose(data)
	case mysql.ComStmtSendLongData:
		return cc.handleStmtSendLongData(data)
	case mysql.ComStmtReset:
		return cc.handleStmtReset(data)
	case mysql.ComSetOption:
		return cc.handleSetOption(data)
	default:
		return mysql.NewErrf(mysql.ErrUnknown, "command %d not supported now", cmd)
	}
}

// dispatch handles client request based on command which is the first byte of the data.
// It also gets a token from server which is used to limit the concurrently handling clients.
// The most frequently used command is ComQuery.
func (cc *clientConn) dispatch(data []byte) error {
	cmd := data[0]
	data = data[1:]
	cc.lastCmd = hack.String(data)

	token := cc.server.getToken()

	startTS := time.Now()
	defer func() {
		cc.server.releaseToken(token)
		log.Debugf("[TIME_CMD] %v %d", time.Since(startTS), cmd)
	}()

	switch cmd {
	case mysql.ComSleep:
		// TODO: According to mysql document, this command is supposed to be used only internally.
		// So it's just a temp fix, not sure if it's done right.
		// Investigate this command and write test case later.
		return nil
	case mysql.ComQuit:
		return io.EOF
	case mysql.ComQuery: // Most frequently used command.
		return cc.handleQuery(hack.String(data))
	case mysql.ComPing:
		return cc.writeOK()
	case mysql.ComInitDB:
		log.Debug("init db", hack.String(data))
		if err := cc.useDB(hack.String(data)); err != nil {
			return errors.Trace(err)
		}
		return cc.writeOK()
	case mysql.ComFieldList:
		return cc.handleFieldList(hack.String(data))
	case mysql.ComStmtPrepare:
		return cc.handleStmtPrepare(hack.String(data))
	case mysql.ComStmtExecute:
		return cc.handleStmtExecute(data)
	case mysql.ComStmtClose:
		return cc.handleStmtClose(data)
	case mysql.ComStmtSendLongData:
		return cc.handleStmtSendLongData(data)
	case mysql.ComStmtReset:
		return cc.handleStmtReset(data)
	case mysql.ComSetOption:
		return cc.handleSetOption(data)
	default:
		return mysql.NewErrf(mysql.ErrUnknown, "command %d not supported now", cmd)
	}
}

func (cc *clientConn) dispatch(data []byte) error {
	cmd := data[0]
	data = data[1:]
	cc.lastCmd = hack.String(data)

	token := cc.server.getToken()

	defer func() {
		cc.server.releaseToken(token)
	}()

	switch cmd {
	case mysql.ComQuit:
		return io.EOF
	case mysql.ComQuery:
		return cc.handleQuery(hack.String(data))
	case mysql.ComPing:
		return cc.writeOK()
	case mysql.ComInitDB:
		log.Debug("init db", hack.String(data))
		if err := cc.useDB(hack.String(data)); err != nil {
			return errors.Trace(err)
		}
		return cc.writeOK()
	case mysql.ComFieldList:
		return cc.handleFieldList(hack.String(data))
	case mysql.ComStmtPrepare:
		return cc.handleStmtPrepare(hack.String(data))
	case mysql.ComStmtExecute:
		return cc.handleStmtExecute(data)
	case mysql.ComStmtClose:
		return cc.handleStmtClose(data)
	case mysql.ComStmtSendLongData:
		return cc.handleStmtSendLongData(data)
	case mysql.ComStmtReset:
		return cc.handleStmtReset(data)
	default:
		msg := fmt.Sprintf("command %d not supported now", cmd)
		return mysql.NewError(mysql.ErUnknownError, msg)
	}
}

func (d *Datum) compareBytes(b []byte) (int, error) {
	return d.compareString(hack.String(b))
}

// GetMysqlSet gets mysql.Set value
func (d *Datum) GetMysqlSet() mysql.Set {
	return mysql.Set{Value: uint64(d.i), Name: hack.String(d.b)}
}

// GetMysqlEnum gets mysql.Enum value
func (d *Datum) GetMysqlEnum() mysql.Enum {
	return mysql.Enum{Value: uint64(d.i), Name: hack.String(d.b)}
}

// GetString gets string value.
func (d *Datum) GetString() string {
	return hack.String(d.b)
}

//.........这里部分代码省略.........
				args[i] = uint64(paramValues[pos])
			} else {
				args[i] = int64(paramValues[pos])
			}

			pos++
			continue

		case mysql.TypeShort, mysql.TypeYear:
			if len(paramValues) < (pos + 2) {
				err = mysql.ErrMalformPacket
				return
			}
			valU16 := binary.LittleEndian.Uint16(paramValues[pos : pos+2])
			if isUnsigned {
				args[i] = uint64(valU16)
			} else {
				args[i] = int64(valU16)
			}
			pos += 2
			continue

		case mysql.TypeInt24, mysql.TypeLong:
			if len(paramValues) < (pos + 4) {
				err = mysql.ErrMalformPacket
				return
			}
			valU32 := binary.LittleEndian.Uint32(paramValues[pos : pos+4])
			if isUnsigned {
				args[i] = uint64(valU32)
			} else {
				args[i] = int64(valU32)
			}
			pos += 4
			continue

		case mysql.TypeLonglong:
			if len(paramValues) < (pos + 8) {
				err = mysql.ErrMalformPacket
				return
			}
			valU64 := binary.LittleEndian.Uint64(paramValues[pos : pos+8])
			if isUnsigned {
				args[i] = valU64
			} else {
				args[i] = int64(valU64)
			}
			pos += 8
			continue

		case mysql.TypeFloat:
			if len(paramValues) < (pos + 4) {
				err = mysql.ErrMalformPacket
				return
			}

			args[i] = float64(math.Float32frombits(binary.LittleEndian.Uint32(paramValues[pos : pos+4])))
			pos += 4
			continue

		case mysql.TypeDouble:
			if len(paramValues) < (pos + 8) {
				err = mysql.ErrMalformPacket
				return
			}

			args[i] = math.Float64frombits(binary.LittleEndian.Uint64(paramValues[pos : pos+8]))
			pos += 8
			continue

		case mysql.TypeDecimal, mysql.TypeNewDecimal, mysql.TypeVarchar,
			mysql.TypeBit, mysql.TypeEnum, mysql.TypeSet, mysql.TypeTinyBlob,
			mysql.TypeMediumBlob, mysql.TypeLongBlob, mysql.TypeBlob,
			mysql.TypeVarString, mysql.TypeString, mysql.TypeGeometry,
			mysql.TypeDate, mysql.TypeNewDate,
			mysql.TypeTimestamp, mysql.TypeDatetime, mysql.TypeDuration:
			if len(paramValues) < (pos + 1) {
				err = mysql.ErrMalformPacket
				return
			}

			v, isNull, n, err = parseLengthEncodedBytes(paramValues[pos:])
			pos += n
			if err != nil {
				return
			}

			if !isNull {
				args[i] = hack.String(v)
			} else {
				args[i] = nil
			}
			continue
		default:
			err = errUnknownFieldType.Gen("stmt unknown field type %d", tp)
			return
		}
	}
	return
}

func (d *Datum) compareBytes(sc *variable.StatementContext, b []byte) (int, error) {
	return d.compareString(sc, hack.String(b))
}