29.12.14.2 Performance Schema variables_info Table (original) (raw)

29.12.14.2 Performance Schema variables_info Table

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

The variables_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, or USER.
  • 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.
• MAX_VALUE
  The maximum permitted value for the variable. For a variable whose type is not numeric, this is always 0.
• 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 are user17 and host34.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.

The variables_info table has no indexes.

TRUNCATE TABLE is not permitted for the variables_info table.

If a variable with a VARIABLE_SOURCE value other than DYNAMIC 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 or DYNAMIC.

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 or SERVER 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 |  
+--------------------------+  

• Join variables_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         |  
+--------------------------+----------------+-----------+-----------+