Bug:http://bugs.mysql.com/bug.php?id=70692

INSERT INTO t2(XXX) SELECT XXX FROM t1;

导致t2的自增值不连续

原因:innodb_autoinc_lock_mode=1引起的，待详细研究
http://dev.mysql.com/doc/refman/5.5/en/innodb-auto-increment-handling.html