innodb_index_stats がデータをインポートするときにテーブルの主キーの競合を促すエラーの詳細な説明

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)

-- 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 */;

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