MySQL Lock--gap before rec insert intention waiting

准备测试数据：

## 创建测试表
CREATE TABLE `tb1001` (
  `order_id` int(11) NOT NULL,
  `order_num` int(11) DEFAULT NULL,
  `order_type` int(11) DEFAULT NULL,
  PRIMARY KEY (`order_id`),
  KEY `idx_order_type` (`order_type`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

## 准备测试数据
insert into tb1001(order_id,order_num,order_type)
values(1,10,1),(2,10,2),(3,10,1),(4,10,2);

先执行事务(事务132868)：

BEGIN;
update tb1001 
set order_num=20 
where order_type=2;

再执行事务(事务ID 132869)：

BEGIN;
update tb1001 
set order_type=2 
where order_id=3;

查看事务锁和阻塞信息

SELECT * FROM INNODB_LOCK_WAITS \G
*************************** 1. row ***************************
requesting_trx_id: 132869
requested_lock_id: 132869:41:4:5
  blocking_trx_id: 132868
 blocking_lock_id: 132868:41:4:5
 
 
select * from INNODB_LOCKS \G
*************************** 1. row ***************************
    lock_id: 132869:41:4:5
lock_trx_id: 132869
  lock_mode: X,GAP
  lock_type: RECORD
 lock_table: `db002`.`tb1001`
 lock_index: idx_order_type
 lock_space: 41
  lock_page: 4
   lock_rec: 5
  lock_data: 2, 4
*************************** 2. row ***************************
    lock_id: 132868:41:4:5
lock_trx_id: 132868
  lock_mode: X
  lock_type: RECORD
 lock_table: `db002`.`tb1001`
 lock_index: idx_order_type
 lock_space: 41
  lock_page: 4
   lock_rec: 5
  lock_data: 2, 4

事务132868上锁信息：

---TRANSACTION 132868, ACTIVE 177 sec
3 lock struct(s), heap size 1136, 5 row lock(s), undo log entries 2
MySQL thread id 3, OS thread handle 140397285517056, query id 14 127.0.0.1 admin
TABLE LOCK table `db002`.`tb1001` trx id 132868 lock mode IX

RECORD LOCKS space id 41 page no 4 n bits 72 index idx_order_type of table `db002`.`tb1001` trx id 132868 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 3 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 80000002; asc     ;;
 1: len 4; hex 80000002; asc     ;;

Record lock, heap no 5 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 80000002; asc     ;;
 1: len 4; hex 80000004; asc     ;;

RECORD LOCKS space id 41 page no 3 n bits 72 index PRIMARY of table `db002`.`tb1001` trx id 132868 lock_mode X locks rec but not gap
Record lock, heap no 3 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 4; hex 80000002; asc     ;;
 1: len 6; hex 000000020704; asc       ;;
 2: len 7; hex 24000000230a28; asc $   # (;;
 3: len 4; hex 80000014; asc     ;;
 4: len 4; hex 80000002; asc     ;;

Record lock, heap no 5 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 4; hex 80000004; asc     ;;
 1: len 6; hex 000000020704; asc       ;;
 2: len 7; hex 24000000230a49; asc $   # I;;
 3: len 4; hex 80000014; asc     ;;
 4: len 4; hex 80000002; asc     ;;

事务132869上锁信息：

---TRANSACTION 132869, ACTIVE 167 sec updating or deleting
mysql tables in use 1, locked 1
LOCK WAIT 3 lock struct(s), heap size 1136, 3 row lock(s), undo log entries 1
MySQL thread id 4, OS thread handle 140397285246720, query id 20 127.0.0.1 admin updating
update tb1001 set order_type=2 where order_id=3
------- TRX HAS BEEN WAITING 6 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 41 page no 4 n bits 72 index idx_order_type of table `db002`.`tb1001` trx id 132869 lock_mode X locks gap before rec insert intention waiting
Record lock, heap no 5 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 80000002; asc     ;;
 1: len 4; hex 80000004; asc     ;;

------------------
TABLE LOCK table `db002`.`tb1001` trx id 132869 lock mode IX
RECORD LOCKS space id 41 page no 3 n bits 72 index PRIMARY of table `db002`.`tb1001` trx id 132869 lock_mode X locks rec but not gap
Record lock, heap no 4 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
 0: len 4; hex 80000003; asc     ;;
 1: len 6; hex 000000020705; asc       ;;
 2: len 7; hex 250000002407c6; asc %   $  ;;
 3: len 4; hex 8000000a; asc     ;;
 4: len 4; hex 80000002; asc     ;;

RECORD LOCKS space id 41 page no 4 n bits 72 index idx_order_type of table `db002`.`tb1001` trx id 132869 lock_mode X locks gap before rec insert intention waiting
Record lock, heap no 5 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 80000002; asc     ;;
 1: len 4; hex 80000004; asc     ;;

MySQL Lock--gap before rec insert intention waiting

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