func (c *Conn) handleOKPacket(data []byte) (*mysql.Result, error) {
	var n int
	var pos int = 1

	r := new(mysql.Result)

	r.AffectedRows, _, n = mysql.LengthEncodedInt(data[pos:])
	pos += n
	r.InsertId, _, n = mysql.LengthEncodedInt(data[pos:])
	pos += n

	if c.capability&mysql.CLIENT_PROTOCOL_41 > 0 {
		r.Status = binary.LittleEndian.Uint16(data[pos:])
		c.status = r.Status
		pos += 2

		//todo:strict_mode, check warnings as error
		//Warnings := binary.LittleEndian.Uint16(data[pos:])
		//pos += 2
	} else if c.capability&mysql.CLIENT_TRANSACTIONS > 0 {
		r.Status = binary.LittleEndian.Uint16(data[pos:])
		c.status = r.Status
		pos += 2
	}

	//info
	return r, nil
}

//build select result with group by opt
func (c *ClientConn) buildSelectGroupByResult(rs []*mysql.Result,
	stmt *sqlparser.Select) (*mysql.Result, error) {
	var err error
	var r *mysql.Result
	var groupByIndexs []int

	fieldLen := len(rs[0].Fields)
	startIndex := fieldLen - len(stmt.GroupBy)
	for startIndex < fieldLen {
		groupByIndexs = append(groupByIndexs, startIndex)
		startIndex++
	}

	funcExprs := c.getFuncExprs(stmt)
	if len(funcExprs) == 0 {
		r, err = c.mergeGroupByWithoutFunc(rs, groupByIndexs)
	} else {
		r, err = c.mergeGroupByWithFunc(rs, groupByIndexs, funcExprs)
	}
	if err != nil {
		return nil, err
	}

	//build result
	names := make([]string, 0, 2)
	if 0 < len(r.Values) {
		r.Fields = r.Fields[:groupByIndexs[0]]
		for i := 0; i < len(r.Fields) && i < groupByIndexs[0]; i++ {
			names = append(names, string(r.Fields[i].Name))
		}
		//delete group by columns in Values
		for i := 0; i < len(r.Values); i++ {
			r.Values[i] = r.Values[i][:groupByIndexs[0]]
		}
		r.Resultset, err = c.buildResultset(r.Fields, names, r.Values)
		if err != nil {
			return nil, err
		}
	} else {
		r.Resultset = c.newEmptyResultset(stmt)
	}

	return r, nil
}

func (c *ClientConn) mergeExecResult(rs []*mysql.Result) error {
	r := new(mysql.Result)
	for _, v := range rs {
		r.Status |= v.Status
		r.AffectedRows += v.AffectedRows
		if r.InsertId == 0 {
			r.InsertId = v.InsertId
		} else if r.InsertId > v.InsertId {
			//last insert id is first gen id for multi row inserted
			//see http://dev.mysql.com/doc/refman/5.6/en/information-functions.html#function_last-insert-id
			r.InsertId = v.InsertId
		}
	}

	if r.InsertId > 0 {
		c.lastInsertId = int64(r.InsertId)
	}
	c.affectedRows = int64(r.AffectedRows)

	return c.writeOK(r)
}

func (c *Conn) readResultRows(result *mysql.Result, isBinary bool) (err error) {
	var data []byte

	for {
		data, err = c.readPacket()

		if err != nil {
			return
		}

		// EOF Packet
		if c.isEOFPacket(data) {
			if c.capability&mysql.CLIENT_PROTOCOL_41 > 0 {
				//result.Warnings = binary.LittleEndian.Uint16(data[1:])
				//todo add strict_mode, warning will be treat as error
				result.Status = binary.LittleEndian.Uint16(data[3:])
				c.status = result.Status
			}

			break
		}

		result.RowDatas = append(result.RowDatas, data)
	}

	result.Values = make([][]interface{}, len(result.RowDatas))

	for i := range result.Values {
		result.Values[i], err = result.RowDatas[i].Parse(result.Fields, isBinary)

		if err != nil {
			return err
		}
	}

	return nil
}

func (c *ClientConn) loadResultWithFuncIntoMap(rs []*mysql.Result,
	groupByIndexs []int, funcExprs map[int]string) (map[string]*ResultRow, error) {

	resultMap := make(map[string]*ResultRow)
	rt := new(mysql.Result)
	rt.Resultset = new(mysql.Resultset)
	rt.Fields = rs[0].Fields

	//change Result into map
	for _, r := range rs {
		for i := 0; i < len(r.Values); i++ {
			keySlice := r.Values[i][groupByIndexs[0]:]
			mk, err := c.generateMapKey(keySlice)
			if err != nil {
				return nil, err
			}

			if v, ok := resultMap[mk]; ok {
				//init rt
				rt.Values = nil
				rt.RowDatas = nil

				//append v and r into rt, and calculate the function value
				rt.Values = append(rt.Values, r.Values[i], v.Value)
				rt.RowDatas = append(rt.RowDatas, r.RowDatas[i], v.RowData)
				resultTmp := []*mysql.Result{rt}

				for funcIndex, funcName := range funcExprs {
					funcValue, err := c.calFuncExprValue(funcName, resultTmp, funcIndex)
					if err != nil {
						return nil, err
					}
					//set the function value in group by
					resultMap[mk].Value[funcIndex] = funcValue
				}
			} else { //key is not exist
				resultMap[mk] = &ResultRow{
					Value:   r.Values[i],
					RowData: r.RowDatas[i],
				}
			}
		}
	}

	return resultMap, nil
}

func (c *Conn) readResultColumns(result *mysql.Result) (err error) {
	var i int = 0
	var data []byte

	for {
		data, err = c.readPacket()
		if err != nil {
			return
		}

		// EOF Packet
		if c.isEOFPacket(data) {
			if c.capability&mysql.CLIENT_PROTOCOL_41 > 0 {
				//result.Warnings = binary.LittleEndian.Uint16(data[1:])
				//todo add strict_mode, warning will be treat as error
				result.Status = binary.LittleEndian.Uint16(data[3:])
				c.status = result.Status
			}

			if i != len(result.Fields) {
				err = mysql.ErrMalformPacket
			}

			return
		}

		result.Fields[i], err = mysql.FieldData(data).Parse()
		if err != nil {
			return
		}

		result.FieldNames[string(result.Fields[i].Name)] = i

		i++
	}
}