refactor ExecuteUpdateResponse

import io.shardingsphere.proxy.backend.common.jdbc.execute.response.unit.ExecuteResponseUnit;

import io.shardingsphere.proxy.backend.common.jdbc.execute.response.unit.ExecuteUpdateResponseUnit;

import io.shardingsphere.proxy.transport.common.packet.DatabasePacket;

import io.shardingsphere.proxy.transport.mysql.packet.command.reponse.CommandResponsePackets;

import io.shardingsphere.proxy.transport.mysql.packet.generic.OKPacket;

import lombok.Getter;

public final class ExecuteUpdateResponse implements ExecuteResponse {

    @Getter

    private final List<DatabasePacket> packets = new LinkedList<>();

    private final List<OKPacket> packets = new LinkedList<>();

    public ExecuteUpdateResponse(final DatabasePacket packet) {

    public ExecuteUpdateResponse(final OKPacket packet) {

        packets.add(packet);

    }

    public CommandResponsePackets merge() {

        int affectedRows = 0;

        long lastInsertId = 0;

        for (DatabasePacket each : packets) {

            if (each instanceof OKPacket) {

                OKPacket okPacket = (OKPacket) each;

                affectedRows += okPacket.getAffectedRows();

        for (OKPacket each : packets) {

            affectedRows += each.getAffectedRows();

            // TODO consider about insert multiple values

                lastInsertId = okPacket.getLastInsertId();

            }

            lastInsertId = each.getLastInsertId();

        }

        return new CommandResponsePackets(new OKPacket(1, affectedRows, lastInsertId));

    }