call mtr.add_suppression("192.0.2.4");
flush status;
flush hosts;
flush user_resources;
flush privileges;
select @@global.debug;
@@global.debug

select @@global.max_connect_errors;
@@global.max_connect_errors
100
select @@global.max_user_connections;
@@global.max_user_connections
0
select @@global.max_connections;
@@global.max_connections
151
select `User`, `Host` from mysql.`user` where `host` like '%\\%%';
User	Host
select `User`, `Host` from mysql.`user` where `user` like '192.%';
User	Host
select `User`, `Host` from mysql.`user` where `user` like '2001:%';
User	Host
select `User`, `Host` from mysql.`user` where `user` like 'santa.claus.%';
User	Host
CREATE USER 'user4'@'santa.claus.ipv4.example.com';
GRANT SELECT ON test.* TO 'user4'@'santa.claus.ipv4.example.com';
SET global debug= "+d,vio_peer_addr_fake_ipv4,getnameinfo_fake_ipv4,getaddrinfo_fake_good_ipv4";
SELECT "Con4 is alive" AS "";

Con4 is alive
SELECT current_user() AS "";

user4@santa.claus.ipv4.example.com
SET global debug= default;

====================================================================
Testing index for columns IP
====================================================================
############ Explain for Query ####################################
explain select SUM_CONNECT_ERRORS 
from performance_schema.host_cache 
where IP = "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 SUM_CONNECT_ERRORS
from performance_schema.host_cache
where IP > "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	host_cache	NULL	ALL	PRIMARY	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select SUM_CONNECT_ERRORS
from performance_schema.host_cache
where IP < "2";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	host_cache	NULL	ALL	PRIMARY	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select SUM_CONNECT_ERRORS
from performance_schema.host_cache
where IP = "192.0.2.4";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	host_cache	NULL	const	PRIMARY	PRIMARY	258	const	#	100.00	NULL
############# Explain End #########################################
flush status;
select SUM_CONNECT_ERRORS
from performance_schema.host_cache
where IP = "192.0.2.4";
SUM_CONNECT_ERRORS
#
OK: handler_read_key incremented

====================================================================
Testing index for columns HOST
====================================================================
############ Explain for Query ####################################
explain select SUM_CONNECT_ERRORS 
from performance_schema.host_cache 
where HOST = "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	host_cache	NULL	ref	HOST	HOST	258	const	#	100.00	NULL
############ Explain for Query ####################################
explain select SUM_CONNECT_ERRORS
from performance_schema.host_cache
where HOST > "impossible";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	host_cache	NULL	ALL	HOST	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select SUM_CONNECT_ERRORS
from performance_schema.host_cache
where HOST < "2";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	host_cache	NULL	ALL	HOST	NULL	NULL	NULL	#	33.33	Using where
############ Explain for Query ####################################
explain select SUM_CONNECT_ERRORS
from performance_schema.host_cache
where HOST = "santa.claus.ipv4.example.com";
id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
1	SIMPLE	host_cache	NULL	ref	HOST	HOST	258	const	#	100.00	NULL
############# Explain End #########################################
flush status;
select SUM_CONNECT_ERRORS
from performance_schema.host_cache
where HOST = "santa.claus.ipv4.example.com";
SUM_CONNECT_ERRORS
#
OK: handler_read_key incremented
REVOKE SELECT ON test.* FROM 'user4'@'santa.claus.ipv4.example.com';
DROP USER 'user4'@'santa.claus.ipv4.example.com';