innodb - MySQL auto increment column -

i see weird behavior auto-increment column number increasing in step of 2 instead of 1. end row ids 1, 3, 5, 7. use mysql 5.6 + innodb engine. idea why weirdness?

mysql> select version(); +-----------------+ | version()       | +-----------------+ | 5.6.20-68.0-log | +-----------------+ 1 row in set (0.00 sec)  mysql> show create table temp_table; | superset_version | create table `temp_table` (   `_id` int(11) not null auto_increment comment 'comm1',   `name` varchar(100) not null comment 'comm2',   `start_time` bigint(20) not null comment 'comm3',   `updated_at` bigint(20) not null comment 'comm4',   `status` varchar(50) not null comment 'comm5',   primary key (`_id`) ) engine=innodb auto_increment=27 default charset=utf8 | 

notice insert incremented _id column difference of 2.

mysql> insert superset_version(name, start_time, updated_at, status) value("temp row", -1, -1, "erro");     query ok, 1 row affected, 1 warning (0.00 sec)  mysql> select * superset_version order _id desc limit 3; +-----+----------+------------+------------+--------+ | _id | name     | start_time | updated_at | status | +-----+----------+------------+------------+--------+ |  33 | temp row |         -1 |         -1 | erro   | |  31 | temp row |         -1 |         -1 | erro   | |  29 | temp row |         -1 |         -1 | erro   | +-----+----------+------------+------------+--------+ 3 rows in set (0.00 sec) 

auto_increment_increment setting set 2, therefore mysql increases auto increment numbers 2. use show varibles ... command check setting.