path: root/mysql-test/r/events_1.result

call mtr.add_suppression("Column count of mysql.event is wrong. Expected .*, found .*\. The table is probably corrupted");
drop database if exists events_test;
drop database if exists db_x;
drop database if exists mysqltest_db2;
drop database if exists mysqltest_no_such_database;
create database events_test;
use events_test;
CREATE USER pauline@localhost;
CREATE DATABASE db_x;
GRANT EVENT ON db_x.* TO pauline@localhost;
USE db_x;
CREATE TABLE x_table(a int);
CREATE EVENT e_x1 ON SCHEDULE EVERY 1 SECOND DO DROP DATABASE db_x;
CREATE EVENT e_x2 ON SCHEDULE EVERY 1 SECOND DO DROP TABLE x_table;
SHOW DATABASES LIKE 'db_x';
Database (db_x)
db_x
SET GLOBAL event_scheduler=1;
SHOW DATABASES LIKE 'db_x';
Database (db_x)
db_x
SHOW TABLES FROM db_x;
Tables_in_db_x
x_table
SET GLOBAL event_scheduler=off;
DROP EVENT e_x1;
DROP EVENT e_x2;
DROP DATABASE db_x;
DROP USER pauline@localhost;
USE events_test;
SET GLOBAL event_scheduler=off;
drop event if exists event1;
Warnings:
Note	1305	Event event1 does not exist
create event event1 on schedule every 15 minute starts now() ends date_add(now(), interval 5 hour) DO begin end;
alter event event1 rename to event2 enable;
alter event event2 disable;
alter event event2 enable;
alter event event2 on completion not preserve;
alter event event2 on schedule every 1 year on completion preserve rename to event3 comment "new comment" do begin select 1; end__
alter event event3 rename to event2;
drop event event2;
create event event2 on schedule every 2 second starts now() ends date_add(now(), interval 5 hour) comment "some" DO begin end;
drop event event2;
CREATE EVENT event_starts_test ON SCHEDULE EVERY 10 SECOND COMMENT "" DO SELECT 1;
SELECT interval_field, interval_value, body FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
interval_field	interval_value	body
SECOND	10	SELECT 1
SELECT execute_at IS NULL, starts IS NULL, ends IS NULL, comment FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
execute_at IS NULL	starts IS NULL	ends IS NULL	comment
1	0	1	
ALTER EVENT event_starts_test ON SCHEDULE AT '2020-02-02 20:00:02';
SELECT execute_at IS NULL, starts IS NULL, ends IS NULL, comment FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
execute_at IS NULL	starts IS NULL	ends IS NULL	comment
0	1	1	
ALTER EVENT event_starts_test COMMENT "non-empty comment";
SELECT execute_at IS NULL, starts IS NULL, ends IS NULL, comment FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
execute_at IS NULL	starts IS NULL	ends IS NULL	comment
0	1	1	non-empty comment
ALTER EVENT event_starts_test COMMENT "";
SELECT execute_at IS NULL, starts IS NULL, ends IS NULL, comment FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
execute_at IS NULL	starts IS NULL	ends IS NULL	comment
0	1	1	
DROP EVENT event_starts_test;
CREATE EVENT event_starts_test ON SCHEDULE EVERY 20 SECOND STARTS '2020-02-02 20:00:02' ENDS '2022-02-02 20:00:02' DO SELECT 2;
SELECT execute_at IS NULL, starts IS NULL, ends IS NULL, comment FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
execute_at IS NULL	starts IS NULL	ends IS NULL	comment
1	0	0	
ALTER EVENT event_starts_test COMMENT "non-empty comment";
SELECT execute_at IS NULL, starts IS NULL, ends IS NULL, comment FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
execute_at IS NULL	starts IS NULL	ends IS NULL	comment
1	0	0	non-empty comment
ALTER EVENT event_starts_test COMMENT "";
SELECT execute_at IS NULL, starts IS NULL, ends IS NULL, comment FROM mysql.event WHERE db='events_test' AND name='event_starts_test';
execute_at IS NULL	starts IS NULL	ends IS NULL	comment
1	0	0	
DROP EVENT event_starts_test;
create table test_nested(a int);
create event e_43 on schedule every 1 second do set @a = 5;
alter event e_43 do alter event e_43 do set @a = 4;
ERROR HY000: Recursion of EVENT DDL statements is forbidden when body is present
alter event e_43 do
begin
alter event e_43 on schedule every 5 minute;
insert into test_nested values(1);
end|
set global event_scheduler = on;
select db, name, body, status, interval_field, interval_value from mysql.event;
db	name	body	status	interval_field	interval_value
events_test	e_43	begin
alter event e_43 on schedule every 5 minute;
insert into test_nested values(1);
end	ENABLED	MINUTE	5
drop event e_43;
drop table test_nested;
"Let's check whether we can use non-qualified names"
create table non_qualif(a int);
create event non_qualif_ev on schedule every 10 minute do insert into non_qualif values (800219);
select * from non_qualif;
a
800219
drop event non_qualif_ev;
drop table non_qualif;
alter event non_existant rename to non_existant_too;
ERROR HY000: Unknown event 'non_existant'
set global event_scheduler = off;
create event existant on schedule at now() + interval 1 year do select 12;
alter event non_existant rename to existant;
ERROR HY000: Event 'existant' already exists
alter event existant rename to events_test.existant;
ERROR HY000: Same old and new event name
drop event existant;
create table t_event3 (a int, b float);
drop event if exists event3;
Warnings:
Note	1305	Event event3 does not exist
create event event3 on schedule every 50 + 10 minute starts date_add("20100101", interval 5 minute) ends date_add("20151010", interval 5 day) comment "portokala_comment" DO insert into t_event3 values (unix_timestamp(), rand());
select count(*) from t_event3;
count(*)
0
drop event event3;
drop table t_event3;
set names utf8;
CREATE EVENT root6 ON SCHEDULE EVERY '10:20' MINUTE_SECOND ON COMPLETION PRESERVE ENABLE COMMENT 'some comment' DO select 1;
SHOW CREATE EVENT root6;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root6		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root6` ON SCHEDULE EVERY '10:20' MINUTE_SECOND STARTS '#' ON COMPLETION PRESERVE ENABLE COMMENT 'some comment' DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root7 on schedule every 2 year do select 1;
SHOW CREATE EVENT root7;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root7		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root7` ON SCHEDULE EVERY 2 YEAR STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root8 on schedule every '2:5' year_month do select 1;
SHOW CREATE EVENT root8;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root8		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root8` ON SCHEDULE EVERY '2-5' YEAR_MONTH STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root8_1 on schedule every '2:15' year_month do select 1;
SHOW CREATE EVENT root8_1;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root8_1		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root8_1` ON SCHEDULE EVERY '3-3' YEAR_MONTH STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root9 on schedule every 2 week ON COMPLETION PRESERVE DISABLE COMMENT 'коментар на кирилица' do select 1;
SHOW CREATE EVENT root9;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root9		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root9` ON SCHEDULE EVERY 2 WEEK STARTS '#' ON COMPLETION PRESERVE DISABLE COMMENT 'коментар на кирилица' DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root10 on schedule every '20:5' day_hour do select 1;
SHOW CREATE EVENT root10;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root10		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root10` ON SCHEDULE EVERY '20 5' DAY_HOUR STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root11 on schedule every '20:25' day_hour do select 1;
SHOW CREATE EVENT root11;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root11		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root11` ON SCHEDULE EVERY '21 1' DAY_HOUR STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root12 on schedule every '20:25' hour_minute do select 1;
SHOW CREATE EVENT root12;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root12		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root12` ON SCHEDULE EVERY '20:25' HOUR_MINUTE STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root13 on schedule every '25:25' hour_minute do select 1;
SHOW CREATE EVENT root13;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root13		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root13` ON SCHEDULE EVERY '25:25' HOUR_MINUTE STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root13_1 on schedule every '11:65' hour_minute do select 1;
SHOW CREATE EVENT root13_1;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root13_1		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root13_1` ON SCHEDULE EVERY '12:5' HOUR_MINUTE STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root14 on schedule every '35:35' minute_second do select 1;
SHOW CREATE EVENT root14;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root14		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root14` ON SCHEDULE EVERY '35:35' MINUTE_SECOND STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root15 on schedule every '35:66' minute_second do select 1;
SHOW CREATE EVENT root15;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root15		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root15` ON SCHEDULE EVERY '36:6' MINUTE_SECOND STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root16 on schedule every '35:56' day_minute do select 1;
SHOW CREATE EVENT root16;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root16		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root16` ON SCHEDULE EVERY '1 11:56' DAY_MINUTE STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root17 on schedule every '35:12:45' day_minute do select 1;
SHOW CREATE EVENT root17;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root17		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root17` ON SCHEDULE EVERY '35 12:45' DAY_MINUTE STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root17_1 on schedule every '35:25:65' day_minute do select 1;
SHOW CREATE EVENT root17_1;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root17_1		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root17_1` ON SCHEDULE EVERY '36 2:5' DAY_MINUTE STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root18 on schedule every '35:12:45' hour_second do select 1;
SHOW CREATE EVENT root18;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root18		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root18` ON SCHEDULE EVERY '35:12:45' HOUR_SECOND STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root19 on schedule every '15:59:85' hour_second do select 1;
SHOW CREATE EVENT root19;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root19		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root19` ON SCHEDULE EVERY '16:0:25' HOUR_SECOND STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
create event root20 on schedule every '50:20:12:45' day_second do select 1;
SHOW CREATE EVENT root20;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
root20		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `root20` ON SCHEDULE EVERY '50 20:12:45' DAY_SECOND STARTS '#' ON COMPLETION NOT PRESERVE ENABLE DO select 1	utf8	utf8_general_ci	latin1_swedish_ci
set names cp1251;
create event ðóóò21 on schedule every '50:23:59:95' day_second COMMENT 'òîâà å 1251 êîìåíòàð' do select 1;
SHOW CREATE EVENT ðóóò21;
Event	sql_mode	time_zone	Create Event	character_set_client	collation_connection	Database Collation
ðóóò21		SYSTEM	CREATE DEFINER=`root`@`localhost` EVENT `руут21` ON SCHEDULE EVERY '51 0:0:35' DAY_SECOND STARTS '#' ON COMPLETION NOT PRESERVE ENABLE COMMENT 'това е 1251 коментар' DO select 1	cp1251	cp1251_general_ci	latin1_swedish_ci
insert into mysql.event (
db,
name,
body,
definer,
interval_value,
interval_field,
originator,
character_set_client,
collation_connection,
db_collation,
body_utf8)
values (
database(),
"root22",
"select 1",
user(),
100,
"SECOND_MICROSECOND",
1,
'utf8',
'utf8_general_ci',
'utf8_general_ci',
'select 1');
show create event root22;
ERROR 42000: This version of MariaDB doesn't yet support 'MICROSECOND'
SHOW EVENTS;
ERROR 42000: This version of MariaDB doesn't yet support 'MICROSECOND'
drop event root22;
create event root23 on schedule every -100 year do select 1;
ERROR HY000: INTERVAL is either not positive or too big
create event root23 on schedule every 222222222222222222222 year do select 1;
ERROR HY000: INTERVAL is either not positive or too big
drop event root6;
drop event root7;
drop event root8;
drop event root8_1;
drop event root9;
drop event root10;
drop event root11;
drop event root12;
drop event root13;
drop event root13_1;
drop event root14;
drop event root15;
drop event root16;
drop event root17;
drop event root17_1;
drop event root18;
drop event root19;
drop event root20;
drop event ðóóò21;
set names latin1;
Create a test event. Only event metadata is relevant, 
the actual schedule and body are not.
CREATE EVENT intact_check ON SCHEDULE EVERY 10 HOUR DO SELECT "nothing";
SHOW EVENTS;
Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status	Originator	character_set_client	collation_connection	Database Collation
events_test	intact_check	root@localhost	SYSTEM	RECURRING	NULL	10	#	#	NULL	ENABLED	1	latin1	latin1_swedish_ci	latin1_swedish_ci
Try to alter mysql.event: the server should fail to load
event information after mysql.event was tampered with.

First, let's add a column to the end and check the error is emitted.

ALTER TABLE mysql.event ADD dummy INT;
SHOW EVENTS;
ERROR HY000: Failed to open mysql.event
SELECT event_name FROM INFORMATION_SCHEMA.events;
ERROR HY000: Failed to open mysql.event
SHOW CREATE EVENT intact_check;
ERROR HY000: Failed to open mysql.event
DROP EVENT no_such_event;
ERROR HY000: Failed to open mysql.event
CREATE EVENT intact_check_1 ON SCHEDULE EVERY 5 HOUR DO SELECT 5;
ERROR HY000: Failed to open mysql.event
ALTER EVENT intact_check_1 ON SCHEDULE EVERY 8 HOUR DO SELECT 8;
ERROR HY000: Failed to open mysql.event
ALTER EVENT intact_check_1 RENAME TO intact_check_2;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check_1;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check_2;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check;
ERROR HY000: Failed to open mysql.event
DROP DATABASE IF EXISTS mysqltest_no_such_database;
Warnings:
Note	1008	Can't drop database 'mysqltest_no_such_database'; database doesn't exist
CREATE DATABASE mysqltest_db2;
DROP DATABASE mysqltest_db2;
Warnings:
Error	1545	Failed to open mysql.event
SELECT @@event_scheduler;
@@event_scheduler
OFF
SHOW VARIABLES LIKE 'event_scheduler';
Variable_name	Value
event_scheduler	OFF
SET GLOBAL event_scheduler=OFF;
ALTER TABLE mysql.event DROP dummy;
DROP EVENT intact_check;
CREATE EVENT intact_check ON SCHEDULE EVERY 10 HOUR DO SELECT "nothing";

Now let's add a column to the first position: the server
expects to see event schema name there

ALTER TABLE mysql.event ADD dummy INT FIRST;
SHOW EVENTS;
ERROR HY000: Failed to open mysql.event
SELECT event_name FROM INFORMATION_SCHEMA.events;
ERROR HY000: Failed to open mysql.event
SHOW CREATE EVENT intact_check;
ERROR HY000: Failed to open mysql.event
DROP EVENT no_such_event;
ERROR HY000: Failed to open mysql.event
CREATE EVENT intact_check_1 ON SCHEDULE EVERY 5 HOUR DO SELECT 5;
ERROR HY000: Failed to open mysql.event
ALTER EVENT intact_check_1 ON SCHEDULE EVERY 8 HOUR DO SELECT 8;
ERROR HY000: Failed to open mysql.event
ALTER EVENT intact_check_1 RENAME TO intact_check_2;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check_1;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check_2;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check;
ERROR HY000: Failed to open mysql.event
DROP DATABASE IF EXISTS mysqltest_no_such_database;
Warnings:
Note	1008	Can't drop database 'mysqltest_no_such_database'; database doesn't exist
CREATE DATABASE mysqltest_db2;
DROP DATABASE mysqltest_db2;
Warnings:
Error	1545	Failed to open mysql.event
SELECT @@event_scheduler;
@@event_scheduler
OFF
SHOW VARIABLES LIKE 'event_scheduler';
Variable_name	Value
event_scheduler	OFF
SET GLOBAL event_scheduler=OFF;
Clean up
ALTER TABLE mysql.event DROP dummy;
DELETE FROM mysql.event;
CREATE EVENT intact_check ON SCHEDULE EVERY 10 HOUR DO SELECT "nothing";
Back up the table, further changes are not reversible
CREATE TABLE event_like LIKE mysql.event;
INSERT INTO event_like SELECT * FROM mysql.event;

Drop some columns and try more checks. 


ALTER TABLE mysql.event DROP comment, DROP starts;
SHOW EVENTS;
ERROR HY000: Failed to open mysql.event
SELECT event_name FROM INFORMATION_SCHEMA.EVENTS;
ERROR HY000: Failed to open mysql.event
SHOW CREATE EVENT intact_check;
ERROR HY000: Failed to open mysql.event
DROP EVENT no_such_event;
ERROR HY000: Failed to open mysql.event
CREATE EVENT intact_check_1 ON SCHEDULE EVERY 5 HOUR DO SELECT 5;
ERROR HY000: Failed to open mysql.event
ALTER EVENT intact_check_1 ON SCHEDULE EVERY 8 HOUR DO SELECT 8;
ERROR HY000: Failed to open mysql.event
ALTER EVENT intact_check_1 RENAME TO intact_check_2;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check_1;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check_2;
ERROR HY000: Failed to open mysql.event
DROP EVENT intact_check;
ERROR HY000: Failed to open mysql.event
DROP DATABASE IF EXISTS mysqltest_no_such_database;
Warnings:
Note	1008	Can't drop database 'mysqltest_no_such_database'; database doesn't exist
CREATE DATABASE mysqltest_db2;
DROP DATABASE mysqltest_db2;
Warnings:
Error	1545	Failed to open mysql.event
SELECT @@event_scheduler;
@@event_scheduler
OFF
SHOW VARIABLES LIKE 'event_scheduler';
Variable_name	Value
event_scheduler	OFF
SET GLOBAL event_scheduler=OFF;

Now drop the table, and test again


DROP TABLE mysql.event;
SHOW EVENTS;
ERROR 42S02: Table 'mysql.event' doesn't exist
SELECT event_name FROM INFORMATION_SCHEMA.events;
ERROR 42S02: Table 'mysql.event' doesn't exist
SHOW CREATE EVENT intact_check;
ERROR 42S02: Table 'mysql.event' doesn't exist
DROP EVENT no_such_event;
ERROR 42S02: Table 'mysql.event' doesn't exist
CREATE EVENT intact_check_1 ON SCHEDULE EVERY 5 HOUR DO SELECT 5;
ERROR 42S02: Table 'mysql.event' doesn't exist
ALTER EVENT intact_check_1 ON SCHEDULE EVERY 8 HOUR DO SELECT 8;
ERROR 42S02: Table 'mysql.event' doesn't exist
ALTER EVENT intact_check_1 RENAME  TO intact_check_2;
ERROR 42S02: Table 'mysql.event' doesn't exist
DROP EVENT intact_check_1;
ERROR 42S02: Table 'mysql.event' doesn't exist
DROP EVENT intact_check_2;
ERROR 42S02: Table 'mysql.event' doesn't exist
DROP EVENT intact_check;
ERROR 42S02: Table 'mysql.event' doesn't exist
DROP DATABASE IF EXISTS mysqltest_no_such_database;
Warnings:
Note	1008	Can't drop database 'mysqltest_no_such_database'; database doesn't exist
CREATE DATABASE mysqltest_db2;
DROP DATABASE mysqltest_db2;
Warnings:
Error	1146	Table 'mysql.event' doesn't exist
OK, there is an unnecessary warning about the non-existent table 
but it's not easy to fix and no one complained about it.
A similar warning is printed if mysql.proc is missing.
SHOW WARNINGS;
Level	Code	Message
Error	1146	Table 'mysql.event' doesn't exist
SELECT @@event_scheduler;
@@event_scheduler
OFF
SHOW VARIABLES LIKE 'event_scheduler';
Variable_name	Value
event_scheduler	OFF
SET GLOBAL event_scheduler=OFF;
Restore the original table.
CREATE TABLE mysql.event like event_like;
DROP TABLE event_like;
SHOW EVENTS;
Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status	Originator	character_set_client	collation_connection	Database Collation

#
# Bug#12394306: the sever may crash if mysql.event is corrupted
#

CREATE EVENT ev1 ON SCHEDULE EVERY 5 HOUR DO SELECT 5;
ALTER EVENT ev1 ON SCHEDULE EVERY 8 HOUR DO SELECT 8;

CREATE TABLE event_original LIKE mysql.event;
INSERT INTO event_original SELECT * FROM mysql.event;

ALTER TABLE mysql.event MODIFY modified CHAR(1);
Warnings:
Warning	1265	Data truncated for column 'modified' at row 1

SHOW EVENTS;
ERROR HY000: Failed to open mysql.event

SELECT event_name, created, last_altered FROM information_schema.events;
ERROR HY000: Failed to open mysql.event

CREATE EVENT ev2 ON SCHEDULE EVERY 5 HOUR DO SELECT 5;
ERROR HY000: Failed to open mysql.event

ALTER EVENT ev1 ON SCHEDULE EVERY 9 HOUR DO SELECT 9;
ERROR HY000: Failed to open mysql.event

DROP TABLE mysql.event;
RENAME TABLE event_original TO mysql.event;

DROP EVENT ev1;

SHOW EVENTS;
Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status	Originator	character_set_client	collation_connection	Database Collation

# 
# End of tests
#
drop database events_test;