【dbdao.com MySQL OCP认证专题】- MySQL 5.6 - OCP 考题讲解 - 12
【dbdao.com MySQL OCP认证专题】- MySQL 5.6 - OCP 考题讲解12.
Which two statements are true about InnoDB auto-increment locking?
A. The auto-increment lock can be a table-level lock.
B. InnoDB never uses table-level locks.
C. Some settings for innodb_autoinc_lock_mode can help reduce locking.
D. InnoDB always protects auto-increment updates with a table-level lock.
E. InnoDB does not use locks to enforce auto-increment uniqueness.
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答案：A, C
分析：
auto-increment的AUTO-INC锁是一个表级锁，因此A正确，B和E错误，。
C正确，根据数据库参数innodb_autoinc_lock_mode的设置，插入操作会根据模式和所用语句的不同选用相应的锁。
innodb_autoinc_lock_mode = 2的时候，将不使用表级锁和轻量mutex锁，不过在基于语句复制(SBR: Statement Based Replication)时，会有交错序列风险。
参考：
http://dev.mysql.com/doc/refman/5.7/en/innodb-auto-increment-handling.html
http://dev.mysql.com/doc/refman/5.7/en/innodb-auto-increment-configurable.html
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