關于innodb_rollback_on_timeout測試

innodb_rollback_on_timeout 
innodb_lock_wait_timeout
最開始看到innodb_rollback_on_timeout 時,沒有好好理解transaction timeout的意思.以為只要是連接超時就會觸發,今天研究了一下.只能說巨坑;
以下測試.隔離級別皆為RR模式.測試過程.

 
實驗一:
innodb_rollback_on_timeout =on
innodb_lock_wait_timeout=20    
---------------------------------------|----------------------------------------|------------------------------------------------
session 1                             |            session 2                   |         session  3   
---------------------------------------|----------------------------------------|------------------------------------------------
 begin;                               |                                        |select * from information_schema.innodb_trx
                                       |                                        |      order by trx_started;   
---------------------------------------|----------------------------------------|------------------------------------------------
insert into t8 values (20,'ddd');      |                                        |       1   
---------------------------------------|----------------------------------------|------------------------------------------------
                                       |            begin;                     |      2   
---------------------------------------|----------------------------------------|------------------------------------------------
                                       | update t8 set test1='yyy' where id =19;|           2   
---------------------------------------|----------------------------------------|------------------------------------------------
                                       |                                        |       2   
update t8 set test1='xxx' where id =19;|                                        |
---------------------------------------|----------------------------------------|------------------------------------------------
               堵塞                    |                                        |          2 
---------------------------------------|----------------------------------------|------------------------------------------------
20s后超時                              |                                        |       1   
事務結束;                              |    commit;                             |     0
---------------------------------------|----------------------------------------|------------------------------------------------     
 

select * from t8;    
20這個id沒有;19被改為yyy;    
  
  
實驗二:
innodb_rollback_on_timeout =off
innodb_lock_wait_timeout=20   
---------------------------------------|---------------------------------------|-----------------------------------------------
                 session 1             |                   session 2          |          session  3   
---------------------------------------|---------------------------------------|-----------------------------------------------
 begin;                               |                                       | select * from information_schema.innodb_trx
                                       |                                       |        order by trx_started;   
---------------------------------------|---------------------------------------|-----------------------------------------------
insert into t8 values (20,'ddd');      |                                       |              1   
---------------------------------------|---------------------------------------|-----------------------------------------------
                                       |                   begin;              |             2   
                                       |update t8 set test1='yyy' where id =19;|
---------------------------------------|---------------------------------------|-----------------------------------------------
update t8 set test1='xxx' where id =19;|                                       |               2
---------------------------------------|---------------------------------------|-----------------------------------------------
堵塞                                   |                                       |               2     
---------------------------------------|---------------------------------------|-----------------------------------------------
20s后超時                              |                                       |              2   
事務未結束                           |                                       |
---------------------------------------|---------------------------------------|-----------------------------------------------
    commit;                            |                       commit;         |               0   
---------------------------------------|---------------------------------------|-----------------------------------------------
  
select * from t8;    
20這個id存在;19被改為yyy;  

結果就是:如果innodb_rollback_on_timeout 為on,事務在innodb_lock_wait_timeout超時后,當前sql會報超時,并使整個事務都回滾,然后結束事務;
         如果innodb_rollback_on_timeout 為off(默認值),事務在innodb_lock_wait_timeout超時后,當前sql會超時,并終止,回滾當前sql,但整個事務不回滾,事務不結束,必須顯示的回滾或提交;
 一句話:innodb_rollback_on_timeout 沒什么卵用.純碎就是坑;