create database explain_test_db;
create table explain_test_db.explain_test_table (c int);
lock table explain_test_db.explain_test_table write;
# Connection con1
insert into explain_test_db.explain_test_table values ('1');
# Connection default
select OBJECT_INSTANCE_BEGIN, NAME, LOCKED_BY_THREAD_ID
from performance_schema.mutex_instances
where LOCKED_BY_THREAD_ID is not NULL
limit 1
into @oib, @name, @lbtid;

====================================================================
Testing index for columns OBJECT_INSTANCE_BEGIN
====================================================================
############ Explain for Query ####################################
explain select count(*) 
from performance_schema.mutex_instances 
where OBJECT_INSTANCE_BEGIN = "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	#	NULL	no matching row in const table
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where OBJECT_INSTANCE_BEGIN > "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ALL	PRIMARY	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where OBJECT_INSTANCE_BEGIN < "2";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ALL	PRIMARY	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where OBJECT_INSTANCE_BEGIN = @oib;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	const	PRIMARY	PRIMARY	8	const	#	100.00	NULL
############# Explain End #########################################
flush status;
select count(*)
from performance_schema.mutex_instances
where OBJECT_INSTANCE_BEGIN = @oib;
count(*)
#
OK: handler_read_key incremented

====================================================================
Testing index for columns NAME
====================================================================
############ Explain for Query ####################################
explain select count(*) 
from performance_schema.mutex_instances 
where NAME = "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ref	NAME	NAME	514	const	#	100.00	NULL
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where NAME > "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ALL	NAME	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where NAME < "2";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ALL	NAME	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where NAME = @name;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ref	NAME	NAME	514	const	#	100.00	NULL
############# Explain End #########################################
flush status;
select count(*)
from performance_schema.mutex_instances
where NAME = @name;
count(*)
#
OK: handler_read_key incremented

====================================================================
Testing index for columns LOCKED_BY_THREAD_ID
====================================================================
############ Explain for Query ####################################
explain select count(*) 
from performance_schema.mutex_instances 
where LOCKED_BY_THREAD_ID = "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ref	LOCKED_BY_THREAD_ID	LOCKED_BY_THREAD_ID	9	const	#	100.00	Using where
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where LOCKED_BY_THREAD_ID > "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ALL	LOCKED_BY_THREAD_ID	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where LOCKED_BY_THREAD_ID < "2";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ALL	LOCKED_BY_THREAD_ID	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select count(*)
from performance_schema.mutex_instances
where LOCKED_BY_THREAD_ID = @lbtid;
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	mutex_instances	NULL	ref	LOCKED_BY_THREAD_ID	LOCKED_BY_THREAD_ID	9	const	#	100.00	Using where
############# Explain End #########################################
flush status;
select count(*)
from performance_schema.mutex_instances
where LOCKED_BY_THREAD_ID = @lbtid;
count(*)
#
OK: handler_read_key incremented
unlock tables;
# connection con1
# connection default
drop table explain_test_db.explain_test_table;
drop database explain_test_db;