SET @save_slave_parallel_threads= @@GLOBAL.slave_parallel_threads;
SELECT IF(COUNT(*) < 20, "OK", CONCAT("Found too many system user processes: ", COUNT(*))) FROM information_schema.processlist WHERE user = "system user";
IF(COUNT(*) < 20, "OK", CONCAT("Found too many system user processes: ", COUNT(*)))
OK
SELECT @@GLOBAL.slave_parallel_threads as 'must be 20 because of .cnf';
must be 20 because of .cnf
20
SELECT @@SESSION.slave_parallel_threads  as 'no session var';
ERROR HY000: Variable 'slave_parallel_threads' is a GLOBAL variable
SET GLOBAL slave_parallel_threads= 0;
SET GLOBAL slave_parallel_threads= DEFAULT;
SELECT @@GLOBAL.slave_parallel_threads as 'must be 0 because of default';
must be 0 because of default
0
SET GLOBAL slave_parallel_threads= 10;
SELECT @@GLOBAL.slave_parallel_threads;
@@GLOBAL.slave_parallel_threads
10
SELECT IF(COUNT(*) < 10, "OK", CONCAT("Found too many system user processes: ", COUNT(*))) FROM information_schema.processlist WHERE user = "system user";
IF(COUNT(*) < 10, "OK", CONCAT("Found too many system user processes: ", COUNT(*)))
OK
SET GLOBAL slave_parallel_threads = @save_slave_parallel_threads;