System variables
CelerData provides many system variables that can be set and modified to suit your requirements. This section describes the variables supported by CelerData. You can view the settings of these variables by running the SHOW VARIABLES command on your MySQL client. You can also use the SET command to dynamically set or modify variables. You can make these variables take effect globally on the entire system, only in the current session, or only in a single query statement.
The variables in CelerData refer to the variable sets in MySQL, but some variables are only compatible with the MySQL client protocol and do not function on the MySQL database.
NOTE
Any user has the privilege to run SHOW VARIABLES and make a variable take effect at session level. However, only users with the SYSTEM-level OPERATE privilege can make a variable take effect globally. Globally effective variables take effect on all the future sessions (excluding the current session).
If you want to make a setting change for the current session and also make that setting change apply to all future sessions, you can make the change twice, once without the
GLOBAL
modifier and once with it. For example:SET query_mem_limit = 137438953472; -- Apply to the current session.
SET GLOBAL query_mem_limit = 137438953472; -- Apply to all future sessions.
View variables
You can view all or some variables by using SHOW VARIABLES [LIKE 'xxx']
. Example:
-- Show all variables in the system.
SHOW VARIABLES;
-- Show variables that match a certain pattern.
SHOW VARIABLES LIKE '%time_zone%';