29.12.14.1 Performance Schema persisted_variables 表
The persisted_variables
table provides an SQL interface to the mysqld-auto.cnf
file that stores persisted global system variable settings, enabling the file contents to be inspected at runtime using SELECT
statements. Variables are persisted using SET PERSIST
or PERSIST_ONLY
statements; see Section 15.7.6.1, “SET Syntax for Variable Assignment”. The table contains a row for each persisted system variable in the file. Variables not persisted do not appear in the table.
The SENSITIVE_VARIABLES_OBSERVER
privilege is required to view the values of sensitive system variables in this table.
For information about persisted system variables, see Section 7.1.9.3, “Persisted System Variables”.
Suppose that mysqld-auto.cnf
looks like this (slightly reformatted):
{
"Version": 1,
"mysql_server": {
"max_connections": {
"Value": "1000",
"Metadata": {
"Timestamp": 1.519921706e+15,
"User": "root",
"Host": "localhost"
}
},
"autocommit": {
"Value": "ON",
"Metadata": {
"Timestamp": 1.519921707e+15,
"User": "root",
"Host": "localhost"
}
}
}
}
Then persisted_variables
has these contents:
mysql> SELECT * FROM performance_schema.persisted_variables;
+-----------------+----------------+
| VARIABLE_NAME | VARIABLE_VALUE |
+-----------------+----------------+
| autocommit | ON |
| max_connections | 1000 |
+-----------------+----------------+
The persisted_variables
table has these columns:
-
VARIABLE_NAME
The variable name listed in
mysqld-auto.cnf
. -
VARIABLE_VALUE
The value listed for the variable in
mysqld-auto.cnf
.
persisted_variables
has these indexes:
-
Primary key on (
VARIABLE_NAME
)
TRUNCATE TABLE
is not permitted for the persisted_variables
table.