Mysql 批量修改四种方式效率对比（一）

Mysql 批量修改四种方式效率对比

环境信息

mysql-5.7.12

mac pro

idea(分配最大内存2g)

测试数据

pom 依赖

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.12</version>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>2.1.2</version>
        </dependency>

        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>

    </dependencies>

数据库

CREATE TABLE `people` (
  `id` bigint(8) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(50) NOT NULL DEFAULT '',
  `last_name` varchar(50) NOT NULL DEFAULT '',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4

初始化测试数据

    //初始化10w数据
    @Test
    void init10wData() {
        for (int i = 0; i < 100000; i++) {
            People people = new People();
            people.setFirstName(UUID.randomUUID().toString());
            people.setLastName(UUID.randomUUID().toString());
            peopleDAO.insert(people);
        }
    }

批量修改方案

第一种 for

    <!-- 批量更新第一种方法，通过接收传进来的参数list进行循环着组装sql -->
    <update id="updateBatch" parameterType="java.util.List">
        <foreach collection="list" item="item" index="index" open="" close="" separator=";">
            update people
            <set>
                <if test="item.firstName != null">
                    first_name = #{item.firstName,jdbcType=VARCHAR},
                </if>
                <if test="item.lastName != null">
                    last_name = #{item.lastName,jdbcType=VARCHAR},
                </if>
            </set>
            where id = #{item.id,jdbcType=BIGINT}
        </foreach>
    </update>

第二种 case when

    <!-- 批量更新第二种方法，通过 case when语句变相的进行批量更新 -->
    <update id="updateBatch2" parameterType="java.util.List">
        update people
        <trim prefix="set" suffixOverrides=",">
            <trim prefix="first_name = case" suffix="end,">
                <foreach collection="list" item="i" index="index">
                    <if test="i.firstName!=null">
                        when id=#{i.id} then #{i.firstName}
                    </if>
                </foreach>
            </trim>
            <trim prefix="last_name = case" suffix="end,">
                <foreach collection="list" item="i" index="index">
                    <if test="i.lastName!=null">
                        when id=#{i.id} then #{i.lastName}
                    </if>
                </foreach>
            </trim>
        </trim>
        where id in
        <foreach collection="list" index="index" item="item" separator="," open="(" close=")">
            #{item.id,jdbcType=BIGINT}
        </foreach>
    </update>

第三种 replace into

<!-- 批量更新第三种方法，通过 replace into  -->
<update id="updateBatch3" parameterType="java.util.List">
    replace into people
    (id,first_name,last_name) values
    <foreach collection="list" index="index" item="item" separator=",">
        (#{item.id},
        #{item.firstName},
        #{item.lastName})
    </foreach>
</update>

第四种 ON DUPLICATE KEY UPDATE

    <!-- 批量更新第四种方法，通过 duplicate key update  -->
    <update id="updateBatch4" parameterType="java.util.List">
        insert into people
        (id,first_name,last_name) values
        <foreach collection="list" index="index" item="item" separator=",">
            (#{item.id},
            #{item.firstName},
            #{item.lastName})
        </foreach>
        ON DUPLICATE KEY UPDATE
        id=values(id),first_name=values(first_name),last_name=values(last_name)
    </update>

测试代码

/**
 * PeopleDAO继承基类
 */
@Mapper
@Repository
public interface PeopleDAO extends MyBatisBaseDao<People, Long> {

    void updateBatch(@Param("list") List<People> list);

    void updateBatch2(List<People> list);

    void updateBatch3(List<People> list);

    void updateBatch4(List<People> list);
}

    @Test
    void updateBatch() {
        List<People> list = new ArrayList<>();
        int loop = 100;
        int count = 100000;
        Long maxCost = 0L;//最长耗时
        Long minCost = Long.valueOf(Integer.MAX_VALUE);//最短耗时
        System.out.println("开始");
        Long startTime = System.currentTimeMillis();

        for (int j = 0; j < count; j++) {
            People people = new People();
            people.setId(ThreadLocalRandom.current().nextLong(0, 100000));
            people.setFirstName(UUID.randomUUID().toString());
            people.setLastName(UUID.randomUUID().toString());
            list.add(people);
        }

        for (int i = 0; i < loop; i++) {
            Long curStartTime = System.currentTimeMillis();
            peopleDAO.updateBatch4(list);
            Long curCostTime = System.currentTimeMillis() - curStartTime;
            if (maxCost < curCostTime) {
                maxCost = curCostTime;
            }
            if (minCost > curCostTime) {
                minCost = curCostTime;
            }
            System.out.println("耗时-" + (System.currentTimeMillis() - curStartTime));
        }
        System.out.println("结束");
        System.out.println("平均-" + (System.currentTimeMillis() - startTime) / loop + "ms");
        System.out.println("最小-" + minCost + "ms");
        System.out.println("最大-" + maxCost + "ms");
    }

效率比较

总结

sql语句for循环效率其实相当高的，因为它仅仅有一个循环体，只不过最后update语句比较多，量大了就有可能造成sql阻塞。

case when虽然最后只会有一条更新语句，但是xml中的循环体有点多，每一个case when 都要循环一遍list集合，所以大批量拼sql的时候会比较慢，所以效率问题严重。使用的时候建议分批插入。

duplicate key update可以看出来是最快的，但是一般大公司都禁用，公司一般都禁止使用replace into和INSERT INTO … ON DUPLICATE KEY UPDATE，这种sql有可能会造成数据丢失和主从上表的自增id值不一致。而且用这个更新时，记得一定要加上id，而且values（）括号里面放的是数据库字段，不是java对象的属性字段

参考文章：

mybatis批量更新数据三种方法效率对比 https://blog.csdn.net/q957967519/article/details/88669552

MySql中4种批量更新的方法 https://blog.csdn.net/weixin_42290280/article/details/89384741