Row lock analysis and deadlock

One 、 Row lock

clear through InnoDB_row_lock State variables are used to analyze the contention of row locks on the system ：

show status like'innodb_row_lock%';

The description of each state quantity is as follows ：
Innodb_row_lock_current_waits: The number of currently waiting locks
Innodb_row_lock_time: The total length of time from system startup to lock up
Innodb_row_lock_time_avg: The average time it takes to wait
Innodb_row_lock_time_max： The longest waiting time from system startup to now
Innodb_row_lock_waits: The total number of times the system has been waiting since it was started

For this 5 Two state variables , The more important thing is ：
Innodb_row_lock_time_avg （ Average waiting time ）
Innodb_row_lock_waits （ Total waiting times ）
Innodb_row_lock_time（ The total waiting time ）

Especially when waiting times are high , And every time the waiting time is not small , We need an analysis system Why is there so much waiting in , Then according to the results of the analysis to develop optimization plan .

Two 、 Deadlock

Set transaction level to mysql Default level ：

set tx_isolation='repeatable-read'; 

Session_1 perform ：

select * from account where id=1 for update; 

Session_2 perform ：

select * from account where id=2 for update; 

Session_1 perform ：

select * from account where id=2 for update; 

Session_2 perform ：

select * from account where id=1 for update;

In most cases mysql Deadlock can be detected automatically and the transaction that generated the deadlock can be rolled back , But in some cases mysql Can't automatically detect deadlocks

Check the recent deadlock log information ：

show engine innodb status\G;