2012/12/20某业务合服后在唯一索引键上出现了重复键现象:
mysql> select count(RoleGID) from RoleData_0;
+----------------+
| count(RoleGID) |
+----------------+
| 41255 |
+----------------+
1 row in set (0.00 sec)
mysql> select count(distinct RoleGID) from RoleData_0;
+-------------------------+
| count(distinct RoleGID) |
+-------------------------+
| 41123 |
+-------------------------+
1 row in set (0.00 sec)
【问题回顾】
【原因分析】
理论上，mysql会保证唯一索引上记录不会重复。
源码跟踪定位原因如下：
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