InnoDB事務鎖之行鎖-insert唯一二級索引重復鍵加鎖案例
阿新 • • 發佈:2018-02-10
action page com 是什麽 inno row error form query 1、表結構
CREATE TABLE `t3` (
`id` int(11) NOT NULL,
`id2` int(11) DEFAULT NULL,
`id3` int(11) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `id2` (`id2`,`id3`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
2、數據
mysql> select *from t3; +----+------+------+ | id | id2 | id3 | +----+------+------+ | 6 | 1 | 1 | | 8 | 1 | 2 | | 10 | 1 | 3 | | 7 | 4 | 4 | | 1 | 6 | 6 | | 4 | 7 | 7 | +----+------+------+ 6 rows in set (0.00 sec)
3、插入數據
mysql> insert into t3 values(11,1,3);
ERROR 1062 (23000): Duplicate entry ‘1-3‘ for key ‘id2‘
4、show engine innodb status\G
---TRANSACTION 17751, ACTIVE 17 sec 2 lock struct(s), heap size 320, 1 row lock(s) MySQL thread id 10, OS thread handle 0xa32ffb90, query id 193 localhost root init show engine innodb status TABLE LOCK table `yzs`.`t3` trx id 17751 lock mode IX RECORD LOCKS space id 30 page no 4 n bits 80 index `id2` of table `yzs`.`t3` trx id 17751 lock mode S Record lock, heap no 7 PHYSICAL RECORD: n_fields 3; compact format; info bits 0 0: len 4; hex 80000001; asc ;; 1: len 4; hex 80000003; asc ;; 2: len 4; hex 8000000a; asc ;;
5、加鎖原理圖
6、總結
唯一二級索引重復鍵檢查中,如果遇到重復key,那麽會對重復的key加S類型的next-key鎖。註意:這裏不論是什麽隔離級別加的都是next-key鎖
InnoDB事務鎖之行鎖-insert唯一二級索引重復鍵加鎖案例