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 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.
For information about persisted system variables, see SET Syntax for Variable Assignment.
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.