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出现的问题（多主自增长ID重复）
1:首先我们通过A,B的test表结构
2:掉A，在B上对数据表test(存在自增长ID)执行插入操作，返回插入ID为1
3:后停掉B，在A上对数据表test(存在自增长ID)执行插入操作，返回的插入ID也是1
4:然后 我们同时启动A,B，就会出现主键ID重复
解决方法：
我们只要保证两台服务器上插入的自增长数据不同就可以了
如：A查奇数ID，B插偶数ID，当然如果服务器多的话，你可以定义算法，只要不同就可以了
在这里我们在A,B上加入参数，以实现奇偶插入
A：my.cnf上加入参数
auto_increment_offset = 1
auto_increment_increment = 2
这样A的auto_increment字段产生的数值是：1, 3, 5, 7, …等奇数ID了
B：my.cnf上加入参数
auto_increment_offset = 2
auto_increment_increment = 2
这样B的auto_increment字段产生的数值是：2, 4, 6, 8, …等偶数ID了
可以看出，你的auto_increment字段在不同的服务器之间绝对不会重复，所以Master-Master结构就没有任何问题了。当然，你还可以使用3台，4台，或者N台服务器，只要保证auto_increment_increment = N 再设置一下auto_increment_offset为适当的初始值就可以了，那样，我们的MySQL可以同时有几十台主服务器，而不会出现自增长ID 重复。bitsCN.com
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