Global Variables

This section describes the ClustrixDB global and session variables. All variables are global. Some variables may also be set at the session level. Session variables override the global setting for the duration of a specific session and are noted below.

Displaying Variable Values

To display values for global or session variables, use the following syntax:

SHOW [GLOBAL | SESSION] VARIABLES [LIKE pattern] 
SHOW  GLOBAL            VARIABLES [LIKE pattern] [WITH DEFAULTS]

The WITH DEFAULTS option shows whether the variable is DEFAULTED, which specifies that the global variable will always be set to the default value recommended by Clustrix. If Clustrix determines that a variable's value should be set to a different default value, variables with DEFAULTED = 1 will automatically be modified as part of an upgrade.

Finding Non-Default Globals 

The following query will list of variables whose values differ from the default, excluding variables whose values are not subject to defaults:

sql> SELECT name, value, default_value 
     FROM system.global_variables 
     JOIN system.global_variable_definitions USING (name)      
     WHERE value != default_value
     AND name NOT IN
          ('cluster_id', 'cluster_name', 'clustrix_version', 'customer_name', 'format_version', 
           'global_variables_ignored_version', 'license', 'mysql_port', 'server_id', 
           'ssl_cert', 'ssl_key', 'view_strmaps_upgraded');

Setting Variable Values

To set a global or session variable to a specific value:

To modify a global variable to always use the Clustrix-recommended default value (DEFAULTED = 1):  

sql> SET GLOBAL variable_name = DEFAULT; 

To set a global variable to a default value with DEFAULTED = 0:

If a session system variable is modified, the value remains in effect within your session until the session ends or the variable is set to another value. No other sessions are affected.

If you change a global variable, the value is applied to new sessions, but not sessions that are already open (including the session where the SET GLOBAL statement occurred). 

Global Variables