MySQL Pokaż status tabeli, autoinkrementacja nie jest poprawna

To funkcja... nie błąd.

Statystyki tabeli są buforowane. Aby wyłączyć pamięć podręczną i zawsze mieć najnowszą wersję, należy zmienić zmienną serwera, która wskazuje czas trwania czyszczenia pamięci podręcznej na 0:

SET PERSIST information_schema_stats_expiry = 0

Domyślna wartość tej właściwości została zmieniona na 86400 (24 godziny) w Mysql 8.x

Przykład:

SET PERSIST information_schema_stats_expiry = 86400
-- 86400 is the default value of mysql 8.x  if you have never changed this you don't need to set this


show variables like 'information_schema_stats_expiry';

+---------------------------------+-------+
| Variable_name                   | Value |
+---------------------------------+-------+
| information_schema_stats_expiry | 86400 |
+---------------------------------+-------+

create schema mytest;

create table `test` (
    `id` int(5) not null auto_increment,
    `name` varchar(256),
    PRIMARY KEY(`id`)
);

insert into test values(null,'name1')
insert into test values(null,'name2')
insert into test values(null,'name3')

show table status where name like 'test';
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time         | Update_time         | Check_time | Collation          | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| test | InnoDB |      10 | Dynamic    |    3 |           5461 |       16384 |               0 |            0 |         0 |              4 | 2018-10-09 15:32:15 | 2018-10-09 15:32:16 | NULL       | utf8mb4_0900_ai_ci |     NULL |                |         |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
-- The Auto_increment field is correctly set to 4.. but is now cached.

insert into test values(null,'name3');

show table status where name like 'test';
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time         | Update_time         | Check_time | Collation          | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| test | InnoDB |      10 | Dynamic    |    3 |           5461 |       16384 |               0 |            0 |         0 |              4 | 2018-10-09 15:32:15 | 2018-10-09 15:32:16 | NULL       | utf8mb4_0900_ai_ci |     NULL |                |         |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
-- The Auto_increment is still 4 (it was cached).

drop schema mytest

Teraz zmieniamy konfigurację:

SET PERSIST information_schema_stats_expiry = 0

i przeprowadzamy ten sam test:

show variables like 'information_schema_stats_expiry'


+---------------------------------+-------+
| Variable_name                   | Value |
+---------------------------------+-------+
| information_schema_stats_expiry | 0     |
+---------------------------------+-------+

create schema mytest;
create table `test` (
    `id` int(5) not null auto_increment,
    `name` varchar(256),
    PRIMARY KEY(`id`)
);

insert into test values(null,'name1');
insert into test values(null,'name2');
insert into test values(null,'name3');

show table status where name like 'test';

+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time         | Update_time         | Check_time | Collation          | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| test | InnoDB |      10 | Dynamic    |    3 |           5461 |       16384 |               0 |            0 |         0 |              4 | 2018-10-09 15:32:49 | 2018-10-09 15:32:49 | NULL       | utf8mb4_0900_ai_ci |     NULL |                |         |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
--  Auto_increment is 4, but the result is not cached!

insert into test values(null,'name3');



show table status where name like 'test';


+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time         | Update_time         | Check_time | Collation          | Checksum | Create_options | Comment |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| test | InnoDB |      10 | Dynamic    |    4 |           4096 |       16384 |               0 |            0 |         0 |              5 | 2018-10-09 15:32:49 | 2018-10-09 15:32:49 | NULL       | utf8mb4_0900_ai_ci |     NULL |                |         |
+------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
-- The  Auto_increment field is now 5 (a correct, not cached value)

drop schema mytest;