VARIABLES_INFO
VARIABLES_INFO
可用于查看当前 TiDB 集群或实例的系统变量默认值、当前值以及作用域等信息。
USE information_schema;
DESC variables_info;
+-----------------+---------------------+------+------+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+---------------------+------+------+---------+-------+
| VARIABLE_NAME | varchar(64) | NO | | NULL | |
| VARIABLE_SCOPE | varchar(64) | NO | | NULL | |
| DEFAULT_VALUE | varchar(64) | NO | | NULL | |
| CURRENT_VALUE | varchar(64) | NO | | NULL | |
| MIN_VALUE | bigint(64) | YES | | NULL | |
| MAX_VALUE | bigint(64) unsigned | YES | | NULL | |
| POSSIBLE_VALUES | varchar(256) | YES | | NULL | |
| IS_NOOP | varchar(64) | NO | | NULL | |
+-----------------+---------------------+------+------+---------+-------+
8 rows in set (0.00 sec)
SELECT * FROM variables_info ORDER BY variable_name LIMIT 3;
+-----------------------------------+----------------+---------------+---------------+-----------+-----------+-----------------+---------+
| VARIABLE_NAME | VARIABLE_SCOPE | DEFAULT_VALUE | CURRENT_VALUE | MIN_VALUE | MAX_VALUE | POSSIBLE_VALUES | IS_NOOP |
+-----------------------------------+----------------+---------------+---------------+-----------+-----------+-----------------+---------+
| allow_auto_random_explicit_insert | SESSION,GLOBAL | OFF | OFF | NULL | NULL | NULL | NO |
| auto_increment_increment | SESSION,GLOBAL | 1 | 1 | 1 | 65535 | NULL | NO |
| auto_increment_offset | SESSION,GLOBAL | 1 | 1 | 1 | 65535 | NULL | NO |
+-----------------------------------+----------------+---------------+---------------+-----------+-----------+-----------------+---------+
3 rows in set (0.01 sec)
VARIABLES_INFO
表中列的含义如下:
VARIABLE_NAME
:系统变量名称。VARIABLE_SCOPE
:系统变量的作用域。SESSION
表示当前 session 可见;INSTANCE
表示当前 TiDB 实例可见;GLOBAL
表示集群内可见;NONE
表示全局只读。DEFAULT_VALUE
:系统变量的默认值。CURRENT_VALUE
:系统变量的当前值。如果应用范围中包含SESSION
,则显示当前 session 的值。MIN_VALUE
:数值类型的系统变量允许的最小值。如果变量值为非数值类型,则为 NULL。MAX_VALUE
:数值类型的系统变量允许的最大值。如果变量值为非数值类型,则为 NULL。POSSIBLE_VALUES
:系统变量所有可能的值。如果变量值不可枚举,则为 NULL。IS_NOOP
:是否为noop
的系统变量。