如何理解MYSQL RC模式insert update可能死锁的情况

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涉及的语句为
RC模式下
update根据主键更新和insert
其实这样的问题在RC模式下，要么是简单update问题，要么是insert造成的主键和唯一键检查唯一性时出现问题。
下面以主键问题为列子进行分析一下可能出现的情况。

update  where条件更新为主键，锁结构出现在单行主键上，辅助索引包含隐含锁结构，当前读RC非唯一索引模式没有GAP锁，
insert  插入印象锁，主键和辅助索引上会出现隐含锁结构，

但是在RC模式下没有GAP所以插入印象锁一般不会成为问题


表结构：
+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table   | Create Table                                                                                                                                                                      |
+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| testlll | CREATE TABLE `testlll` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=24 DEFAULT CHARSET=latin1 |
+---------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+


情况1
insert
update


TX1：                                                                  TX2：
insert into testlll(name) values('gaopeng');
                                                                          insert into testlll(name) values('gaopeng');
update testlll set name='gaopeng1' where id=25;(堵塞)
                                                                           update testlll set name='gaopeng1' where id=24;(堵塞)
                                               
死锁

锁结构：

点击(此处)折叠或打开

1. ---TRANSACTION 322809, ACTIVE 30 sec starting index read
   

2. mysql tables in use 1, locked 1
   

3. 3 lock struct(s), heap size 1160, 2 row lock(s), undo log entries 1
   

4. MySQL thread id 3, OS thread handle 140734663714560, query id 409 localhost root updating
   

5. update testlll set name='gaopeng1' where id=24
   

6. ---lock strcut(1):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
   

7. TABLE LOCK table `test`.`testlll` trx id 322809 lock mode IX
   

8. ---lock strcut(2):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
   

9. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 322809 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP)
   

10. Record lock, heap no 25 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

11.  0: len 4; hex 80000019; asc ;;
    

12.  1: len 6; hex 00000004ecf9; asc ;;
    

13.  2: len 7; hex f0000001f90110; asc ;;
    

14.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    
    

15. ---lock strcut(3):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

16. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 322809 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
    

17. Record lock, heap no 20 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

18.  0: len 4; hex 80000018; asc ;;
    

19.  1: len 6; hex 00000004ecf8; asc ;;
    

20.  2: len 7; hex ef000001f80110; asc ;;
    

21.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    
    

22. ---TRANSACTION 322808, ACTIVE 43 sec starting index read
    

23. mysql tables in use 1, locked 1
    

24. LOCK WAIT 3 lock struct(s), heap size 1160, 2 row lock(s), undo log entries 1
    

25. MySQL thread id 2, OS thread handle 140734663980800, query id 408 localhost root updating
    

26. update testlll set name='gaopeng1' where id=25
    

27. ------- TRX HAS BEEN WAITING 5 SEC FOR THIS LOCK TO BE GRANTED:
    

28. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 322808 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
    

29. Record lock, heap no 25 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

30.  0: len 4; hex 80000019; asc ;;
    

31.  1: len 6; hex 00000004ecf9; asc ;;
    

32.  2: len 7; hex f0000001f90110; asc ;;
    

33.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    
    

    ------------------
    

34. ---lock strcut(1):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

35. TABLE LOCK table `test`.`testlll` trx id 322808 lock mode IX
    

36. ---lock strcut(2):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

37. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 322808 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
    

38. Record lock, heap no 25 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

39.  0: len 4; hex 80000019; asc ;;
    

40.  1: len 6; hex 00000004ecf9; asc ;;
    

41.  2: len 7; hex f0000001f90110; asc ;;
    

42.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    
    

43. ---lock strcut(3):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

44. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 322808 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP)
    

45. Record lock, heap no 20 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

46.  0: len 4; hex 80000018; asc ;;
    

47.  1: len 6; hex 00000004ecf8; asc ;;
    

48.  2: len 7; hex ef000001f80110; asc ;;
    

49.  3: len 7; hex 67616f70656e67; asc gaopeng;;

情况2
update
update

TX1：                                                                    TX2：
update testlll set name='gaopeng1' where id=22;
                                                                            update testlll set name='gaopeng1' where id=25;
update testlll set name='gaopeng1' where id=25;(堵塞)
                                                                             update testlll set name='gaopeng1' where id=22;(堵塞)
死锁


这种情况比较简单不打印出锁结构


情况3
insert
insert


TX1：                                                      TX2:
insert into testlll values(26,'gaopeng');
                                                             insert into testlll values(27,'gaopeng');
nsert into testlll values(27,'gaopeng');(堵塞)
                                                             insert into testlll values(26,'gaopeng');(堵塞)


死锁

锁结构:

点击(此处)折叠或打开

1. ---TRANSACTION 422212176315800, not started
   

2. 0 lock struct(s), heap size 1160, 0 row lock(s)
   

3. ---TRANSACTION 323284, ACTIVE 10 sec inserting
   

4. mysql tables in use 1, locked 1
   

5. 3 lock struct(s), heap size 1160, 2 row lock(s), undo log entries 1
   

6. MySQL thread id 2, OS thread handle 140734663980800, query id 369 localhost root update
   

7. insert into testlll values(26,'gaopeng')
   

8. ---lock strcut(1):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
   

9. TABLE LOCK table `test`.`testlll` trx id 323284 lock mode IX
   

10. ---lock strcut(2):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

11. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 323284 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP)
    

12. Record lock, heap no 27 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

13.  0: len 4; hex 8000001b; asc ;;
    

14.  1: len 6; hex 00000004eed4; asc ;;
    

15.  2: len 7; hex d3000002a10110; asc ;;
    

16.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    
    

    
    

17. ---lock strcut(3):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

18. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 323284 lock mode S(LOCK_S) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
    

19. Record lock, heap no 26 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

20.  0: len 4; hex 8000001a; asc ;;
    

21.  1: len 6; hex 00000004eed3; asc ;;
    

22.  2: len 7; hex d2000002330110; asc 3 ;;
    

23.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    
    

    
    

24. ---TRANSACTION 323283, ACTIVE 14 sec inserting
    

25. mysql tables in use 1, locked 1
    

26. LOCK WAIT 3 lock struct(s), heap size 1160, 2 row lock(s), undo log entries 1
    

27. MySQL thread id 3, OS thread handle 140734663714560, query id 368 localhost root update
    

28. insert into testlll values(27,'gaopeng')
    

29. ------- TRX HAS BEEN WAITING 5 SEC FOR THIS LOCK TO BE GRANTED:
    

30. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 323283 lock mode S(LOCK_S) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
    

31. Record lock, heap no 27 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

32.  0: len 4; hex 8000001b; asc ;;
    

33.  1: len 6; hex 00000004eed4; asc ;;
    

34.  2: len 7; hex d3000002a10110; asc ;;
    

35.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    ------------------
    

36. ---lock strcut(1):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

37. TABLE LOCK table `test`.`testlll` trx id 323283 lock mode IX
    

38. ---lock strcut(2):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

39. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 323283 lock mode S(LOCK_S) locks rec but not gap(LOCK_REC_NOT_GAP) waiting(LOCK_WAIT)
    

40. Record lock, heap no 27 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

41.  0: len 4; hex 8000001b; asc ;;
    

42.  1: len 6; hex 00000004eed4; asc ;;
    

43.  2: len 7; hex d3000002a10110; asc ;;
    

44.  3: len 7; hex 67616f70656e67; asc gaopeng;;
    

    
    

45. ---lock strcut(3):(Add by gaopeng) In modify Version I force check all REC_LOCK/TAB_LOCK for this Trx
    

46. RECORD LOCKS space id 434 page no 3 n bits 96 index PRIMARY of table `test`.`testlll` trx id 323283 lock_mode X(LOCK_X) locks rec but not gap(LOCK_REC_NOT_GAP)
    

47. Record lock, heap no 26 PHYSICAL RECORD: n_fields 4; compact format; info bits 0
    

48.  0: len 4; hex 8000001a; asc ;;
    

49.  1: len 6; hex 00000004eed3; asc ;;
    

50.  2: len 7; hex d2000002330110; asc 3 ;;
    

51.  3: len 7; hex 67616f70656e67; asc gaopeng;;

以上就是如何理解MYSQL RC模式insert update可能死锁的情况，小编相信有部分知识点可能是我们日常工作会见到或用到的。希望你能通过这篇文章学到更多知识。更多详情敬请关注亿速云行业资讯频道。