h0099 最近的时间轴更新
h0099

h0099

V2EX 第 323482 号会员,加入于 2018-06-19 02:26:22 +08:00
今日活跃度排名 4943
h0099 最近回复了
如果单独只看您发的那坨`SHOW ENGINE INNODB STATUS`deadlock detection log 的话那当时场景就是
session2 先执行因而持有着`(bid, sid, oid)`
```
RECORD LOCKS space id 270 page no 6338 n bits 352 index idx_bid_sid_oid of table db.tb trx id 7367656999 lock_mode X
Record lock, heap no 1 PHYSICAL RECORD: n_fields 1; compact format; info bits 0 0: len 8; hex 73757072656d756d; asc supremum;;
Record lock, heap no 13 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
```
上的末端`(某值, +∞)`[`nextkey`]( https://dev.mysql.com/doc/refman/5.7/en/innodb-locking.html#innodb-next-key-locks)X 锁因为有[`hex 73757072656d756d; asc supremum`]( https://en.wikipedia.org/wiki/Infimum_and_supremum) https://dev.mysql.com/blog-archive/innodb-data-locking-part-2-5-locks-deeper-dive/

而后执行的 session1 也在尝试 acquire`(bid, sid, oid)=('444444', '555555', '666666')`上的 recordlockX 锁但由于其位于 session2 的`nextkey`X 锁范围中而等待
```
RECORD LOCKS space id 270 page no 6338 n bits 352 index idx_bid_sid_oid of table db.tb trx id 7367657071 lock_mode X waiting Record lock, heap no 13 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
```

当 session1 在等待时 session2 也开始等待 PK (但下面的约束不是在`PRIMARY KEY (id)`上而是`INSERT`中的其他字段可能因为其是`AUTO_INCREMENT`AI 而您也没显式指定其值所以无法`WHERE`)`(bid, sid, oid, emark, amark, bmark, cmark)=('444444', '555555', '666666', '00', '00', '00', '00')`上的[recordlock(有`but not gap`)]( https://dev.mysql.com/doc/refman/5.7/en/innodb-locking.html#innodb-record-locks)X
```
RECORD LOCKS space id 270 page no 7273 n bits 88 index PRIMARY of table db.tb trx id 7367656999 lock_mode X locks rec but not gap waiting
[...]
3: len 25; hex 4f4243574830315a3032363631323032333132323241303536; asc 444444;;
4: len 10; hex 30313939373333303331; asc 555555;;
5: len 6; hex 363733353839; asc 666666;;
[...]
```
所以是互相等待对方而被 deadlock detection 并决定 rollback 后来的 session1 让 session2 先过
```
2023-12-28T19:00:05.140247+08:00 3180165 [Note] InnoDB: *** WE ROLL BACK TRANSACTION (1)
```
如果您能够修改逻辑避免在 sql 中用到`ON DUPLICATE KEY UPDATE`aka 您不是只能加索引调参优化的 dba 而是透过 orm 层层抽象隔离写 java 业务的 dev 那您也可以像您 at 我过来的那帖中那样换成`RC 事务隔离级别`+`SELECT ... WHERE unique 约束或 PK FOR UPDATE`产生`表级 IX 锁` https://github.com/n0099/open-tbm/issues/32#issuecomment-1401223094 对`SELECT`出既有的 record 来`UPDATE ... SET a|emark = ... WHERE unique 约束或 PK`再对不存在的 record 进行`INSERT`此时可以保证`INSERT`不会返回`ERROR 1062 (23000): Duplicate entry`因为此前的`SELECT ... FOR UPDATE`已经上了`表级 IX 锁` https://dev.mysql.com/doc/refman/5.7/en/innodb-locking.html#innodb-intention-locks 而此时其他`INSERT`需要`行级 X 锁`就会阻塞等待`表级 IX 锁`释放
> Before a transaction can acquire an exclusive lock on a row in a table, it must first acquire an IX lock on the table.
首先您 tb2 删漏了
```diff
CREATE TABLE `tb2` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`bid` varchar(38) NOT NULL,
`expire_time` datetime DEFAULT NULL,
`status` char(2) NOT NULL,
`create_time` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
`update_time` datetime DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (`id`),
- UNIQUE KEY `idx_name_list_batch_id` (`batch_id`),
+ UNIQUE KEY `idx_name_bid` (`bid`),
KEY `idx_name_list_expire_time` (`expire_time`),
- KEY `index_name_list_market_no` (`market_case_no`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
```
在 mysql8.0.35 下创建表后
```sql
INSERT INTO tb1(sid, bid, oid, status) VALUES(0, 1, 2, 3);
INSERT INTO tb2(bid, expire_time, status) VALUES(1, ADDDATE(NOW(), 2), 3);
```
默认 RR 事务隔离级别下
```sql
-- session1
START TRANSACTION;
insert into tb(bid, sid, oid, emark, amark, bmark, cmark, update_time) values ('444444', '555555', '666666', '00', '00', '00', '00', now()) ON DUPLICATE KEY UPDATE amark = values(amark), update_time = now();
-- 重复执行
ROLLBACK;
```
```sql
-- session2 您的`'2023-12-31 19:00:03.963'`我改成了`ADDDATE(NOW(), 3)`以便 reprod
START TRANSACTION;
insert into tb(bid, sid, oid, emark, amark, bmark, update_time) select tb1.bid, tb1.sid, tb1.oid, '10', '00', '00', now() from tb1 left join tb2 on tb1.bid = tb2.bid where tb2.expire_time < ADDDATE(NOW(), 3) and tb2.expire_time > now() and tb1.status IN ('2', '3') ON DUPLICATE KEY UPDATE emark = values(emark), update_time = now();
-- 重复执行
ROLLBACK;
```
不论两个谁先执行执行几次它们都不会等待 acquire 另一事务占有的锁
而在 RC 下
|session1|session2|
|-|-|
|`SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;`|Ibid.|
|`START TRANSACTION;`|Ibid.|
|`SHOW SESSION VARIABLES LIKE '%iso%'\G`|Ibid.|
|`insert into tb(bid, sid, oid, emark, amark, bmark, cmark, update_time) values ('444444', '555555', '666666', '00', '00', '00', '00', now()) ON DUPLICATE KEY UPDATE amark = values(amark), update_time = now();`||
||`insert into tb(bid, sid, oid, emark, amark, bmark, update_time) select tb1.bid, tb1.sid, tb1.oid, '10', '00', '00', now() from tb1 left join tb2 on tb1.bid = tb2.bid where tb2.expire_time < ADDDATE(NOW(), 3) and tb2.expire_time > now() and tb1.status IN ('2', '3') ON DUPLICATE KEY UPDATE emark = values(emark), update_time = now();`|
||等待 session1 释放某个锁|
|`ROLLBACK;`||
||继续执行并返回|

而如果 session2 先执行那后续它们以任意顺序执行都不会有等待
这可能是因为`tb`此时作为空表(`CREATE`后没有`INSERT`过) session1`INSERT`后需要表级锁以保证其他事务能够 RC (看到其刚`INSERT`的这行,但由于不是`READ UNCOMMITTED`RU 级别所以需要等待 session1`ROLLBACK`/`COMMIT`)
https://stackoverflow.com/questions/56434878/mysql-deadlock-using-an-index-with-a-new-value/56435470#56435470
> In an empty table, the place that the 1 would have been is "anywhere in the table" (or anywhere from the start to the "supremum" mentioned in the deadlock) - which is consequently gaplocked by the delete. The same is true for the 2. And those locks do not conflict each other by definition.

而在 session2 先`INSERT`后`tb`不是空表所以 session1 无需表级锁而可以在索引`idx_bid_sid`上锁`('444444', '555555')`,而 session2`INSERT SELECT`subquery 所返回行`(bid, sid)=(1, 0)`中也没有跟`('444444', '555555')`冲突因而无需`ON DUPLICATE KEY UPDATE`从而避免等待 session1 释放对那行的锁
所以您的`tb`表在 session1 执行`INSERT`时是空的吗?
事务 2`INSERT INTO tb SELECT ...`的 subquery
```sql
select tb1.bid, tb1.sid, tb1.oid, '10', '00', '00', now()
from tb1 left join tb2
on tb1.bid = tb2.bid
where tb2.expire_time < '2023-12-31 19:00:03.963'
and tb2.expire_time > now()
and tb1.status IN ('2', '3')
```
返回中有没有`(bid, sid, oid)`=`('444444', '555555', '666666')`的行?
https://www.v2ex.com/t/908047#r_14219204
https://www.v2ex.com/t/1005536#r_14219181

我的评价是:建议先大脑升级`最新最热最凶最恶`mysql8.2
#13 @netabare 建议直接使用四叶信安底层壬上壬上海贵族 FSF EFF 精神会员杨博文阁下 @yangbowen 最爱的 GPG PGP 包装信息
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