一条简单SQL语句出现死锁情况，请帮忙各位大神帮忙分析一下。

  • Z时代
  • 2024-01-10
  • 分类：IT

小弟有一SQL语句现在在多并发的情况下会出现死锁。希望各位大神帮忙给小弟分析一下。

UPDATE accountinfo SET usecnt = 20, version = version+1 WHERE usecnt > 0 AND accountid = 12 and version = 102

其中accountid为主键，usecnt和version没有任何索引。
当前事务使用的事务隔离级别为：READ_COMMITTED

发生死锁的日志如下：

*** (1) TRANSACTION:
TRANSACTION 1331664, ACTIVE 40 sec starting index read
mysql tables in use 1, locked 1
LOCK WAIT 11 lock struct(s), heap size 2936, 6 row lock(s), undo log entries 9
MySQL thread id 106, OS thread handle 0x334c, query id 2285 192.168.25.85 root updating
UPDATE accountinfo SET usecnt = 20, version = version+1 
            WHERE usecnt > 0 AND accountid = 12 and version = 102
*** (1) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 2151 page no 3 n bits 80 index `PRIMARY` of table `stamp_server_db`.`accountinfo` trx id 1331664 lock_mode X locks rec but not gap waiting
Record lock, heap no 10 PHYSICAL RECORD: n_fields 35; compact format; info bits 0

*** (2) TRANSACTION:
TRANSACTION 1331673, ACTIVE 39 sec starting index read
mysql tables in use 1, locked 1
11 lock struct(s), heap size 2936, 6 row lock(s), undo log entries 9
MySQL thread id 109, OS thread handle 0x3910, query id 2355 192.168.25.85 root updating
UPDATE accountinfo SET usecnt = 20, version = version+1 
            WHERE usecnt > 0 AND accountid = 12 and version = 102
*** (2) HOLDS THE LOCK(S):
RECORD LOCKS space id 2151 page no 3 n bits 80 index `PRIMARY` of table `stamp_server_db`.`accountinfo` trx id 1331673 lock mode S locks rec but not gap
Record lock, heap no 10 PHYSICAL RECORD: n_fields 35; compact format; info bits 0
*** (2) WAITING FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 2151 page no 3 n bits 80 index `PRIMARY` of table `stamp_server_db`.`accountinfo` trx id 1331673 lock_mode X locks rec but not gap waiting
Record lock, heap no 10 PHYSICAL RECORD: n_fields 35; compact format; info bits 0
*** WE ROLL BACK TRANSACTION (2)

请各位大神，帮小弟看一下。怎么破。

补充：
explain UPDATE accountinfo SET usecnt = 1999, version = version+1 WHERE usecnt > 0 AND accountid = 12 and version = 102

图片描述

回答：

看日志事务2获得了一个共享锁(读锁)，然后这个事务要修改同样的记录时，由于前面给记录上了共享锁，没办法再加排他锁(写锁)，一个事务中不是只有update操作吧。

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