show databases;
Database
information_schema
mtr
mysql
performance_schema
test
select count(*) from performance_schema.performance_timers;
count(*)
5
select count(*) from performance_schema.setup_consumers;
count(*)
12
select count(*) > 3 from performance_schema.setup_instruments;
count(*) > 3
1
select count(*) from performance_schema.setup_timers;
count(*)
4
show engine PERFORMANCE_SCHEMA status;
show status like "performance_schema%";
show variables like "performance_schema_events_waits_history_size";
Variable_name	Value
performance_schema_events_waits_history_size	0
select count(*) from performance_schema.events_waits_history;
count(*)
0
truncate table performance_schema.events_waits_history;