MySQL "Show table status", 自增不正确
MySQL "Show table status", auto increment is not correct
我在 Mysql 中创建了一个新的 table，添加了一些行，但是显示 table 的 Auto_increment 字段仍然 return 为 NULL。
mysql手册说：这个字段应该return："The next Auto_increment value"
https://dev.mysql.com/doc/refman/8.0/en/show-table-status.html
我做错了什么？
如何正确找到下一个 auto_increment 值？
重现步骤：
create table `test` (
`id` int(5) not null auto_increment,
`name` varchar(256),
PRIMARY KEY(`id`)
);
那我运行:
show table status where name like 'test';
结果：
Name, Engine, Version, ..., Auto_increment, ...
'test', 'InnoDB', '10', ..., NULL, ...
那我运行:
insert into test values(null,'name1');
insert into test values(null,'name2');
insert into test values(null,'name3');
编辑：-其他插入语法-
insert into test (name) values('name4');
insert into test (name) values('name5');
insert into test (name) values('name6');
获取 table
的状态
show table status where name like 'test';
结果
Name, Engine, Version, ..., Auto_increment, ...
'test', 'InnoDB', '10', ..., NULL, ...
table
中的数据
select * from test;
结果：
1 name1
2 name2
3 name3
供您参考：
SHOW VARIABLES LIKE "%version%";
结果：
'innodb_version', '8.0.12'
'protocol_version', '10'
'slave_type_conversions', ''
'tls_version', 'TLSv1,TLSv1.1,TLSv1.2'
'version', '8.0.12'
'version_comment', 'MySQL Community Server - GPL'
'version_compile_machine', 'x86_64'
'version_compile_os', 'Win64'
'version_compile_zlib', '1.2.11'
编辑：
自动提交：
SHOW VARIABLES LIKE "autocommit";
结果：
'autocommit', 'ON'
编辑：
一段时间后它会自动开始工作。没有明确的理由如何让它开始工作。
这是一个功能..不是错误。
table 统计信息被缓存。要禁用缓存并始终拥有最新版本，您应该将指示缓存清除持续时间的服务器变量更改为 0：
SET PERSIST information_schema_stats_expiry = 0
此 属性 的默认值已更改为 Mysql 8.x
中的 86400（24 小时）
示例：
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
现在我们更改配置：
SET PERSIST information_schema_stats_expiry = 0
和我们运行一样的测试：
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;
我在 Mysql 中创建了一个新的 table，添加了一些行，但是显示 table 的 Auto_increment 字段仍然 return 为 NULL。
mysql手册说：这个字段应该return："The next Auto_increment value"
https://dev.mysql.com/doc/refman/8.0/en/show-table-status.html
我做错了什么？
如何正确找到下一个 auto_increment 值？
重现步骤：
create table `test` (
`id` int(5) not null auto_increment,
`name` varchar(256),
PRIMARY KEY(`id`)
);
那我运行:
show table status where name like 'test';
结果：
Name, Engine, Version, ..., Auto_increment, ...
'test', 'InnoDB', '10', ..., NULL, ...
那我运行:
insert into test values(null,'name1');
insert into test values(null,'name2');
insert into test values(null,'name3');
编辑：-其他插入语法-
insert into test (name) values('name4');
insert into test (name) values('name5');
insert into test (name) values('name6');
获取 table
的状态show table status where name like 'test';
结果
Name, Engine, Version, ..., Auto_increment, ...
'test', 'InnoDB', '10', ..., NULL, ...
table
中的数据select * from test;
结果：
1 name1
2 name2
3 name3
供您参考：
SHOW VARIABLES LIKE "%version%";
结果：
'innodb_version', '8.0.12'
'protocol_version', '10'
'slave_type_conversions', ''
'tls_version', 'TLSv1,TLSv1.1,TLSv1.2'
'version', '8.0.12'
'version_comment', 'MySQL Community Server - GPL'
'version_compile_machine', 'x86_64'
'version_compile_os', 'Win64'
'version_compile_zlib', '1.2.11'
编辑： 自动提交：
SHOW VARIABLES LIKE "autocommit";
结果：
'autocommit', 'ON'
编辑：
一段时间后它会自动开始工作。没有明确的理由如何让它开始工作。
这是一个功能..不是错误。
table 统计信息被缓存。要禁用缓存并始终拥有最新版本，您应该将指示缓存清除持续时间的服务器变量更改为 0：
SET PERSIST information_schema_stats_expiry = 0
此 属性 的默认值已更改为 Mysql 8.x
中的 86400（24 小时）示例：
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
现在我们更改配置：
SET PERSIST information_schema_stats_expiry = 0
和我们运行一样的测试：
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;