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MySQL 9.3 Reference Manual

29.12.14.3 Performance Schema variables_info Table

Thevariables_info table shows, for each system variable, the source from which it was most recently set, and its range of values.

Thevariables_info table has these columns:

VARIABLE_NAME
The variable name.
VARIABLE_SOURCE
The source from which the variable was most recently set:
- COMMAND_LINE
  The variable was set on the command line.
- COMPILED
  The variable has its compiled-in default value.COMPILED is the value used for variables not set any other way.
- DYNAMIC
  The variable was set at runtime. This includes variables set within files specified using theinit_file system variable.
- EXPLICIT
  The variable was set from an option file named with the--defaults-file option.
- EXTRA
  The variable was set from an option file named with the--defaults-extra-file option.
- GLOBAL
  The variable was set from a global option file. This includes option files not covered byEXPLICIT,EXTRA,LOGIN,PERSISTED,SERVER, orUSER.
- LOGIN
  The variable was set from a user-specific login path file (~/.mylogin.cnf).
- PERSISTED
  The variable was set from a server-specificmysqld-auto.cnf option file. No row has this value if the server was started withpersisted_globals_load disabled.
- SERVER
  The variable was set from a server-specific$MYSQL_HOME/my.cnf option file. For details about howMYSQL_HOME is set, seeSection 6.2.2.2, “Using Option Files”.
- USER
  The variable was set from a user-specific~/.my.cnf option file.
VARIABLE_PATH
If the variable was set from an option file,VARIABLE_PATH is the path name of that file. Otherwise, the value is the empty string.
MIN_VALUE
The minimum permitted value for the variable. For a variable whose type is not numeric, this is always 0.
This column is deprecated, and subject to removal in a future release; instead, use theMIN_VALUE column of thevariables_metadata table to obtain this information.
MAX_VALUE
The maximum permitted value for the variable. For a variable whose type is not numeric, this is always 0.
This column is deprecated, and subject to removal in a future release; instead, use theMAX_VALUE column of thevariables_metadata table to obtain this information.
SET_TIME
The time at which the variable was most recently set. The default is the time at which the server initialized global system variables during startup.
SET_USER,SET_HOST
The user name and host name of the client user that most recently set the variable. If a client connects asuser17 from hosthost34.example.com using the account'user17'@'%.example.com,SET_USER andSET_HOST areuser17 andhost34.example.com, respectively. For proxy user connections, these values correspond to the external (proxy) user, not the proxied user against which privilege checking is performed. The default for each column is the empty string, indicating that the variable has not been set since server startup.

Thevariables_info table has no indexes.

TRUNCATE TABLE is not permitted for thevariables_info table.

If a variable with aVARIABLE_SOURCE value other thanDYNAMIC is set at runtime,VARIABLE_SOURCE becomesDYNAMIC andVARIABLE_PATH becomes the empty string.

A system variable that has only a session value (such asdebug_sync) cannot be set at startup or persisted. For session-only system variables,VARIABLE_SOURCE can be onlyCOMPILED orDYNAMIC.

If a system variable has an unexpectedVARIABLE_SOURCE value, consider your server startup method. For example,mysqld_safe reads option files and passes certain options it finds there as part of the command line that it uses to startmysqld. Consequently, some system variables that you set in option files might display invariables_info asCOMMAND_LINE, rather than asGLOBAL orSERVER as you might otherwise expect.

Some sample queries that use thevariables_info table, with representative output:

Display variables set on the command line:

mysql> SELECT VARIABLE_NAME       FROM performance_schema.variables_info       WHERE VARIABLE_SOURCE = 'COMMAND_LINE'       ORDER BY VARIABLE_NAME;+---------------+| VARIABLE_NAME |+---------------+| basedir       || datadir       || log_error     || pid_file      || plugin_dir    || port          |+---------------+

Display variables set from persistent storage:

mysql> SELECT VARIABLE_NAME       FROM performance_schema.variables_info       WHERE VARIABLE_SOURCE = 'PERSISTED'       ORDER BY VARIABLE_NAME;+--------------------------+| VARIABLE_NAME            |+--------------------------+| event_scheduler          || max_connections          || validate_password.policy |+--------------------------+

Joinvariables_info with theglobal_variables table to display the current values of persisted variables, together with their range of values:

mysql> SELECT         VI.VARIABLE_NAME, GV.VARIABLE_VALUE,         VI.MIN_VALUE,VI.MAX_VALUE       FROM performance_schema.variables_info AS VI         INNER JOIN performance_schema.global_variables AS GV         USING(VARIABLE_NAME)       WHERE VI.VARIABLE_SOURCE = 'PERSISTED'       ORDER BY VARIABLE_NAME;+--------------------------+----------------+-----------+-----------+| VARIABLE_NAME            | VARIABLE_VALUE | MIN_VALUE | MAX_VALUE |+--------------------------+----------------+-----------+-----------+| event_scheduler          | ON             | 0         | 0         || max_connections          | 200            | 1         | 100000    || validate_password.policy | STRONG         | 0         | 0         |+--------------------------+----------------+-----------+-----------+

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