index merge导致死锁问题

Posted 2021-06-13 zincredible

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问题现象

前置条件： m_task 表 m_id和t_id是普通索引

这么一条简单的语句居然可能发生死锁 update m_task set `state`=1 where m_id=1 and t_id=1

org.springframework.dao.DeadlockLoserDataAccessException:
### Error updating database. Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
### The error may exist in file [F:\\idea-prj\\springboot-mybaits-demo\\target\\classes\\mapper\\MTaskInfoMapper.xml]
### The error may involve com.zsk.mybaits.demo.dao.MTaskInfoMapper.updateByPrimaryKeySelective-Inline
### The error occurred while setting parameters
### SQL: update m_task SET `state` = ? where m_id = ? and t_id = ?
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
; Deadlock found when trying to get lock; try restarting transaction; nested exception is com.mysql.jdbc.exceptions.jdbc4.MySQLTransactionRollbackException: Deadlock found when trying to get lock; try restarting transaction
at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:271)
at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:72)
at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:88)

问题重现

建表Sql

CREATE TABLE `m_task` (
`id` bigint(11) NOT NULL AUTO_INCREMENT,
`state` int(4) NULL DEFAULT NULL,
`m_id` bigint(11) NULL DEFAULT NULL,
`t_id` bigint(11) NULL DEFAULT NULL,
PRIMARY KEY (`id`) USING BTREE,
INDEX `m_id`(`m_id`) USING BTREE,
INDEX `t_id`(`t_id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 10008 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;

插入10000条数据每100条m_id对应相同的t_id

@GetMapping("/insertTestData")
public String insert() {
    int index = 1;
    for (int i = 1; i <= 10000; i++) {
        MTaskInfo info = new MTaskInfo();
        info.setMId((long) (i % 100));
        info.setTId((long) (index));
        if (i % 100 == 0) {
            index++;
        }
        taskDao.insert(info);
    }
    return "insert 10000 row data success";
}

测试，多点几次接口

private static ExecutorService pool = Executors.newCachedThreadPool();

@GetMapping("/testDeadLock")
public String getTask() {
    for (int i = 1; i <= 100; i++) {
        final int ii = i;
        pool.execute(() -> {
            int state = (int) (Math.random() * 10);
            System.out.println("update " + ii + "state:" + state);
            MTaskInfo info = new MTaskInfo();
            info.setMId((long) ii);
            info.setTId((long) ii);
            info.setState(state);
            taskDao.updateByPrimaryKeySelective(info);
        });
    }
    return "test success";
}