How to use innodb row locks
This article focuses on "how to use innodb row locks". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to use innodb line locks.
Three levels
Record lock locks a row of records
Gap lock locks records in a certain range
Next key lock is the superposition of the first two effects.
Experimental environment
Mysql > select @ @ tx_isolation
+-+
| | @ @ tx_isolation |
+-+
| | REPEATABLE-READ |
+-+
1 row in set (0.00 sec)
Mysql > select * from t
+-+
| | id |
+-+
| | 2 |
| | 8 |
| | 19 |
| | 22 |
+-+
Mysql > create index t_ind on t (id)
Query OK, 0 rows affected (8.52 sec)
Open two sessions at the same time and open things
Conversation one
Mysql > start transaction
Query OK, 0 rows affected (0.00 sec)
Mysql > delete from t where id=19
Query OK, 1 row affected (0.00 sec)
Conversation two
Mysql > start transaction
Query OK, 0 rows affected (0.00 sec)
Mysql > insert into t values (55)
Query OK, 1 row affected (0.00 sec)
Mysql > insert into t values (10)
^ C ^ C-- query aborted
ERROR 1317 (70100): Query execution was interrupted
Mysql >
Mysql > insert into t values (1)
Query OK, 1 row affected (0.00 sec)
Mysql > insert into t values (12)
^ C ^ C-- query aborted
ERROR 1317 (70100): Query execution was interrupted
Mysql >
Session 2 indicates that between 8-22 is locked and data cannot be inserted. This is gap lock.
Cancel gap lock
Modify the isolation level of things to READ COMMITTED
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