代理模式实现mybatis批量插入更新,优化插入效率

10/23 18:06
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一、问题

数据库mysql,在使用mybatis进行批量插入的时候,报错:### Cause: com.mysql.cj.jdbc.exceptions.PacketTooBigException: Packet for query is too large (4,850,051 > 4,194,304). You can change this value on the server by setting the 'max_allowed_packet' variable.,如:

 
image.png

 

二、原因

在对mysql进行插入、更新或查询操作时,mysql server接收处理的数据包大小是有限制的,如果太大超过了设置的max_allowed_packet参数的大小,会导致操作失败,我们可以通过命令:show VARIABLES like '%max_allowed_packet%';查看参数值,如:

 
image.png

 

三、解决方案

  1. 数据库层面解决:调整max_allowed_packet参数,改大,额,多大合适呢?

  2. 应用层面解决:批量插入时,将入参list进行分割,分批批量插入,控制每次批量插入的大小,避免超过最大限制

我们这里选择第2种解决方案

四、代码实现

1、v0.1版本(每个mapper对应的service方法中,都进行分割处理)
1.1、我们需要用到google提供的方法:Lists.partition()对list进行分割,引入maven:

        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-collections4</artifactId>
            <version>4.1</version>
        </dependency>

1.2、UserMapper.xml

    <insert id="batchInsert" parameterType="list">
        insert into user(username, password)
        values
        <foreach collection="list" item="item" index="index" separator=",">
            (#{item.username}, #{item.password})
        </foreach>
    </insert>

    <insert id="batchUpdate" parameterType="list">
        update user
        <trim prefix="set" suffixOverrides=",">
            <trim prefix="username=case" suffix="end,">
                <foreach collection="list" item="item" index="index">
                    when id = #{item.id} then #{item.username}
                </foreach>
            </trim>
            <trim prefix="password=case" suffix="end,">
                <foreach collection="list" item="item" index="index">
                    when id = #{item.id} then #{item.password}
                </foreach>
            </trim>
        </trim>
        where id in
        <foreach collection="list" item="item" index="index" separator="," open="(" close=")">
            #{item.id}
        </foreach>
    </insert>

1.3、UserServiceImpl

    @Override
    public void batchInsert(List<User> list) {
        if (CollectionUtils.isEmpty(list)) {
            return;
        }

        List<List<User>> partition = Lists.partition(list, MAX_SIZE_PER_TIME);
        for (List<User> batchList : partition) {
            userMapper.batchInsert(batchList);
        }
    }

    @Override
    public void batchUpdate(List<User> list) {
        if (CollectionUtils.isEmpty(list)) {
            return;
        }

        List<List<User>> partition = Lists.partition(list, MAX_SIZE_PER_TIME);
        for (List<User> batchList : partition) {
            userMapper.batchUpdate(batchList);
        }
    }

MAX_SIZE_PER_TIME:即每次最大插入记录数,为方便测试,我这里取3,大家可以根据具体场景、数据库、业务需求指定,没有唯一

其他service以此类推,这样可以实现,但是会发现重复代码一堆,需改进

2、v0.2版本(代理模式实现,对方法进行增强,批量插入前,统一对集合进行分割)
2.1、首先定义一个mapper的批量处理接口:BatchProcessMapper

package com.wangzaiplus.test.service.batch;

import java.util.List;

public interface BatchProcessMapper<T> {

    void batchInsert(List<T> list);

    void batchUpdate(List<T> list);

}

2.2、然后UserMapper等mapper实现BatchProcessMapper

package com.wangzaiplus.test.mapper;

import com.wangzaiplus.test.service.batch.BatchProcessMapper;

public interface UserMapper extends BatchProcessMapper<User> {

}

2.3、然后定义MapperProxy也实现BatchProcessMapper

package com.wangzaiplus.test.service.batch.mapperproxy;

import com.google.common.collect.Lists;
import com.wangzaiplus.test.service.batch.BatchProcessMapper;
import org.apache.commons.collections4.CollectionUtils;

import java.util.List;

import static com.wangzaiplus.test.common.Constant.MAX_SIZE_PER_TIME;

public class MapperProxy<T> implements BatchProcessMapper<T> {

    private BatchProcessMapper batchProcessMapper;

    public MapperProxy(BatchProcessMapper batchProcessMapper) {
        this.batchProcessMapper = batchProcessMapper;
    }

    @Override
    public void batchInsert(List<T> list) {
        if (CollectionUtils.isEmpty(list)) {
            return;
        }

        List<List<T>> partition = Lists.partition(list, MAX_SIZE_PER_TIME);
        for (List<T> batchList : partition) {
            batchProcessMapper.batchInsert(batchList);
        }
    }

    @Override
    public void batchUpdate(List<T> list) {
        if (CollectionUtils.isEmpty(list)) {
            return;
        }

        List<List<T>> partition = Lists.partition(list, MAX_SIZE_PER_TIME);
        for (List<T> batchList : partition) {
            batchProcessMapper.batchUpdate(batchList);
        }
    }

}

2.4、使用:UserServiceImpl中直接调用批量插入方法:

@Service
public class UserServiceImpl implements UserService {

    @Autowired
    private UserMapper userMapper;

    @Override
    public void batchInsert(List<User> list) {
        new MapperProxy<User>(userMapper).batchInsert(list);
    }

    @Override
    public void batchUpdate(List<User> list) {
        new MapperProxy<User>(userMapper).batchUpdate(list);
    }

}

其他service同上,一行代码搞定,省却重复代码

五、mybatis批量插入与更新

1、批量插入:
1.1、语法:

    <insert id="batchInsert" parameterType="list">
        insert into user(username, password)
        values
        <foreach collection="list" item="item" index="index" separator=",">
            (#{item.username}, #{item.password})
        </foreach>
    </insert>

1.2、sql实际执行语句:

 
 
image.png

2、批量更新:
2.1、语法:

    <insert id="batchUpdate" parameterType="list">
        update user
        <trim prefix="set" suffixOverrides=",">
            <trim prefix="username=case" suffix="end,">
                <foreach collection="list" item="item" index="index">
                    when id = #{item.id} then #{item.username}
                </foreach>
            </trim>
            <trim prefix="password=case" suffix="end,">
                <foreach collection="list" item="item" index="index">
                    when id = #{item.id} then #{item.password}
                </foreach>
            </trim>
        </trim>
        where id in
        <foreach collection="list" item="item" index="index" separator="," open="(" close=")">
            #{item.id}
        </foreach>
    </insert>

2.2、sql实际执行语句:

 
 
image.png

格式化一下是这样子:

UPDATE USER
SET username = CASE
WHEN id = ? THEN
    ?
WHEN id = ? THEN
    ?
WHEN id = ? THEN
    ?
END,
 PASSWORD = CASE
WHEN id = ? THEN
    ?
WHEN id = ? THEN
    ?
WHEN id = ? THEN
    ?
END
WHERE
    id IN (?, ?, ?)

434616(Integer), batchUpdate_3366361bc15048129adfcf5dc851d7e5(String), 
434617(Integer), batchUpdate_76370f7c845642f2be0ab1c35440f5bd(String), 
434618(Integer), batchUpdate_6e06394ccbbd49c8b97c3e0600a7cada(String), 

434616(Integer), 123456(String), 
434617(Integer), 123456(String), 
434618(Integer), 123456(String), 

434616(Integer), 
434617(Integer), 
434618(Integer)

六、总结

在使用mybatis批量操作数据库时,需要注意集合大小,太大会导致sql执行异常,所以在批量操作前,应该对集合进行分割处理,然后分批操作,为了减少重复代码,可以通过代理模式对批量处理方法进行增强,客户端调用时只需将具体子类传给代理,由代理在执行批量语句前统一进行分割处理

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