Đó là một tính năng .. không phải là một lỗi.
Bảng thống kê được lưu vào bộ nhớ đệm. Để tắt bộ nhớ cache và luôn có phiên bản mới nhất, bạn nên thay đổi biến máy chủ cho biết khoảng thời gian xóa bộ nhớ cache thành 0:
SET PERSIST information_schema_stats_expiry = 0
Giá trị mặc định của thuộc tính này đã thay đổi thành 86400 (24 giờ) trong Mysql 8.x
Ví dụ:
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
Bây giờ chúng tôi thay đổi cấu hình:
SET PERSIST information_schema_stats_expiry = 0
và chúng tôi chạy cùng một bài kiểm tra:
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;
