mySql Optimization parameters or commands

Query

SHOW GLOBAL STATUS

SHOW VARIABLES LIKE '%size%';
SHOW GLOBAL VARIABLES LIKE '%size%';

Settings

SET GLOBAL join_buffer_size = 1024 * 1024 * 128 #128M

or

[mysqld]
join_buffer_size = 128M  #default ~256K

 

References:

[0] Compute memory http://mysqlcalculator.com/ 

[1] join_buffer_size https://dba.stackexchange.com/questions/74693/how-to-break-table-into-two-without-losing-performance 

[2] https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html

[3] Example tunning https://dba.stackexchange.com/questions/127862/tuning-mysql-variables-to-accommodate-high-load

[4] Query variables https://dev.mysql.com/doc/refman/8.0/en/show-variables.html