innodb_index_stats导入备份数据时报错表主键冲突的解决方法

故障描述

percona5.6，mysqldump全备份，导入备份数据时报错Duplicate entry 'hoc_log99-item_log_27-PRIMARY-n_diff_pfx01' for key 'PRIMARY'

故障原因

查看了下这个主键应该是MySQL系统库下的系统表innodb_index_stats

mysql> show create table innodb_index_stats\G
*************************** 1. row ***************************
    Table: innodb_index_stats
Create Table: CREATE TABLE `innodb_index_stats` (
 `database_name` varchar(64) COLLATE utf8_bin NOT NULL,
 `table_name` varchar(64) COLLATE utf8_bin NOT NULL,
 `index_name` varchar(64) COLLATE utf8_bin NOT NULL,
 `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
 `stat_name` varchar(64) COLLATE utf8_bin NOT NULL,
 `stat_value` bigint(20) unsigned NOT NULL,
 `sample_size` bigint(20) unsigned DEFAULT NULL,
 `stat_description` varchar(1024) COLLATE utf8_bin NOT NULL,
 PRIMARY KEY (`database_name`,`table_name`,`index_name`,`stat_name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin STATS_PERSISTENT=0

1 row in set (0.00 sec)

mysql> select * from innodb_index_stats where database_name='hoc_log99' and table_name='item_log_27' and stat_name='n_diff_pfx01' and index_name='PRIMARY';
+---------------+-------------+------------+---------------------+--------------+------------+-------------+------------------+
| database_name | table_name | index_name | last_update     | stat_name  | stat_value | sample_size | stat_description |
+---------------+-------------+------------+---------------------+--------------+------------+-------------+------------------+
| hoc_log99   | item_log_27 | PRIMARY  | 2016-10-07 18:44:06 | n_diff_pfx01 |   823672 |     20 | redid      |
+---------------+-------------+------------+---------------------+--------------+------------+-------------+------------------+
1 row in set (0.00 sec)

再查看下我当时的备份文件sql的记录，发现再导入这个表之前是会重建表的，排除了再导入这个表之前，有item_log_27 表的操作记录进了innodb_index_stats的可能。

-- Table structure for table `innodb_index_stats`
DROP TABLE IF EXISTS `innodb_index_stats`;
CREATE TABLE `innodb_index_stats` (
-- Dumping data for table `innodb_index_stats`
LOCK TABLES `innodb_index_stats` WRITE;
/*!40000 ALTER TABLE `innodb_index_stats` DISABLE KEYS */;

于是我又查看了下最近的binlog记录，发现确实有重建这个表的操作

DROP TABLE IF EXISTS `innodb_index_stats` /* generated by server */
CREATE TABLE `innodb_index_stats` (
/*!40000 ALTER TABLE `innodb_index_stats` DISABLE KEYS */

结论

mysql 5.6的bug，也有其他同行遇到了一样的错误

https://www.percona.com/forums/questions-discussions/mysql-and-percona-server/31971-mysql-innodb_index_stats-duplication-entry-error-on-restore

https://bugs.mysql.com/bug.PHP?id=71814

解决办法

1 mysqldump添加参数忽略这个表的备份

2 将备份文件中的这个表的insert改为replace

3 mysql -f强制导入

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