mysql 锁

1. 数据库：Mysql中“select … for update”排他锁分析
   https://blog.youkuaiyun.com/claram/article/details/54023216
2. select语句for update作用
   https://blog.youkuaiyun.com/kb5706/article/details/7488521
3. mysql 死锁日志，说的很详细，但不全
   https://mp.weixin.qq.com/s/yzXbbutzVJ1hIZgVszIBgw

先记下，后续再补充

问题：
org.apache.ibatis.exceptions.PersistenceException:

Error querying database. Cause: org.apache.ibatis.executor.BatchExecutorException: com.elex.cok.puredb.dao.UserExchangeCodeMapper.insertBatch (batch index #31) failed. 30 prior sub executor(s) completed successfully, but will be rolled back. Cause: java.sql.BatchUpdateException: Deadlock found when trying to get lock; try restarting transacti

优化：
1、参考竞技场，玩家会母服不删数据
2、j对这几个表，进行单独删除，先查出来，再根据主键key删除