Does transaction release insert intention lock after insertion?

问题

After executing the below code,

create table t(id int primary key);
insert into t values (5),(10);

-- session 1
start transaction;
select * from t where id > 8 for share;

-- session 2
start transaction;
insert into t values(6); -- is blocked

the output of select * from performance_schema.data_locks is:

+--------+---------------------------------------+-----------------------+-----------+----------+---------------+-------------+----------------+-------------------+------------+-----------------------+-----------+------------------------+-------------+------------------------+
| ENGINE | ENGINE_LOCK_ID                        | ENGINE_TRANSACTION_ID | THREAD_ID | EVENT_ID | OBJECT_SCHEMA | OBJECT_NAME | PARTITION_NAME | SUBPARTITION_NAME | INDEX_NAME | OBJECT_INSTANCE_BEGIN | LOCK_TYPE | LOCK_MODE              | LOCK_STATUS | LOCK_DATA              |
+--------+---------------------------------------+-----------------------+-----------+----------+---------------+-------------+----------------+-------------------+------------+-----------------------+-----------+------------------------+-------------+------------------------+
| INNODB | 140043377180872:1063:140043381460688  |                  2132 |        49 |       56 | test          | t           | NULL           | NULL              | NULL       |       140043381460688 | TABLE     | IX                     | GRANTED     | NULL                   |
| INNODB | 140043377180872:2:4:3:140043381457776 |                  2132 |        49 |       56 | test          | t           | NULL           | NULL              | PRIMARY    |       140043381457776 | RECORD    | X,GAP,INSERT_INTENTION | WAITING     | 10                     |
| INNODB | 140043377180024:1063:140043381454544  |       421518353890680 |        48 |      105 | test          | t           | NULL           | NULL              | NULL       |       140043381454544 | TABLE     | IS                     | GRANTED     | NULL                   |
| INNODB | 140043377180024:2:4:1:140043381451552 |       421518353890680 |        48 |      105 | test          | t           | NULL           | NULL              | PRIMARY    |       140043381451552 | RECORD    | S                      | GRANTED     | supremum pseudo-record |
| INNODB | 140043377180024:2:4:3:140043381451552 |       421518353890680 |        48 |      105 | test          | t           | NULL           | NULL              | PRIMARY    |       140043381451552 | RECORD    | S                      | GRANTED     | 10                     |
+--------+---------------------------------------+-----------------------+-----------+----------+---------------+-------------+----------------+-------------------+------------+-----------------------+-----------+------------------------+-------------+------------------------+

We can see that session 2 is waiting for insert intention lock which conflicts with next-key lock (5, 10] being held by session 1. This is what I expect to see. But if I change the schedule to

create table t(id int primary key);
insert into t values (5),(10);

-- session 1
start transaction;
insert into t values(6);

-- session 2
start transaction;
select * from t where id > 8 for share; -- is not blocked

the output of select * from performance_schema.data_locks is:

+--------+---------------------------------------+-----------------------+-----------+----------+---------------+-------------+----------------+-------------------+------------+-----------------------+-----------+-----------+-------------+------------------------+
| ENGINE | ENGINE_LOCK_ID                        | ENGINE_TRANSACTION_ID | THREAD_ID | EVENT_ID | OBJECT_SCHEMA | OBJECT_NAME | PARTITION_NAME | SUBPARTITION_NAME | INDEX_NAME | OBJECT_INSTANCE_BEGIN | LOCK_TYPE | LOCK_MODE | LOCK_STATUS | LOCK_DATA              |
+--------+---------------------------------------+-----------------------+-----------+----------+---------------+-------------+----------------+-------------------+------------+-----------------------+-----------+-----------+-------------+------------------------+
| INNODB | 140043377180024:1063:140043381454544  |                  2147 |        48 |      125 | test          | t           | NULL           | NULL              | NULL       |       140043381454544 | TABLE     | IX        | GRANTED     | NULL                   |
| INNODB | 140043377180872:1063:140043381460688  |       421518353891528 |        49 |       86 | test          | t           | NULL           | NULL              | NULL       |       140043381460688 | TABLE     | IS        | GRANTED     | NULL                   |
| INNODB | 140043377180872:2:4:1:140043381457776 |       421518353891528 |        49 |       86 | test          | t           | NULL           | NULL              | PRIMARY    |       140043381457776 | RECORD    | S         | GRANTED     | supremum pseudo-record |
| INNODB | 140043377180872:2:4:3:140043381457776 |       421518353891528 |        49 |       86 | test          | t           | NULL           | NULL              | PRIMARY    |       140043381457776 | RECORD    | S         | GRANTED     | 10                     |
+--------+---------------------------------------+-----------------------+-----------+----------+---------------+-------------+----------------+-------------------+------------+-----------------------+-----------+-----------+-------------+------------------------+

There is no insert intention lock being held by session 1, so, does transaction release insert intention lock after insertion?

来源：https://stackoverflow.com/questions/62737123/does-transaction-release-insert-intention-lock-after-insertion

标签

mysql

transactions

locking

InnoDB