BUG#16420: Events: timestamps become UTC

BUG#26429: SHOW CREATE EVENT is incorrect for an event that
           STARTS NOW()
BUG#26431: Impossible to re-create an event from backup if its
           STARTS clause is in the past
WL#3698: Events: execution in local time zone

The problem was that local times specified by the user in AT, STARTS
and ENDS of CREATE EVENT/ALTER EVENT statement were converted to UTC,
and the original time zone was forgotten.  This way, event scheduler
couldn't honor Daylight Saving Time shifts, and times shown to the
user were also in UTC.  Additionally, CREATE EVENT didn't allow times
in the past, thus preventing straightforward event restoration from
old backups.

This patch reworks event scheduler time computations, performing them
in the time zone associated with the event.  Also it allows times to
be in the past.

The patch adds time_zone column to mysql.event table.

NOTE: The patch is almost final, but the bug#9953 should be pushed
first.

1 files changed, 16 insertions, 16 deletions

diff --git a/mysql-test/r/mysqldump.result b/mysql-test/r/mysqldump.result
index 0190094f0ba..da90ff2cf6b 100644
--- a/mysql-test/r/mysqldump.result
+++ b/mysql-test/r/mysqldump.result
@@ -3440,35 +3440,35 @@ use first;
 set time_zone = 'UTC';
 create event ee1 on schedule at '2035-12-31 20:01:23' do set @a=5;
 show events;
-Db	Name	Definer	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
-first	ee1	root@localhost	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
+Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
+first	ee1	root@localhost	UTC	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
 show create event ee1;
-Event	sql_mode	Create Event
-ee1		CREATE EVENT `ee1` ON SCHEDULE AT '2035-12-31 20:01:23' ON COMPLETION NOT PRESERVE ENABLE DO set @a=5
+Event	sql_mode	time_zone	Create Event
+ee1		UTC	CREATE EVENT `ee1` ON SCHEDULE AT '2035-12-31 20:01:23' ON COMPLETION NOT PRESERVE ENABLE DO set @a=5
 drop database first;
 create database second;
 use second;
 show events;
-Db	Name	Definer	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
-second	ee1	root@localhost	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
+Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
+second	ee1	root@localhost	UTC	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
 show create event ee1;
-Event	sql_mode	Create Event
-ee1	NO_AUTO_VALUE_ON_ZERO	CREATE EVENT `ee1` ON SCHEDULE AT '2035-12-31 20:01:23' ON COMPLETION NOT PRESERVE ENABLE DO set @a=5
+Event	sql_mode	time_zone	Create Event
+ee1	NO_AUTO_VALUE_ON_ZERO	UTC	CREATE EVENT `ee1` ON SCHEDULE AT '2035-12-31 20:01:23' ON COMPLETION NOT PRESERVE ENABLE DO set @a=5
 create event ee2 on schedule at '2018-12-31 21:01:23' do set @a=5;
 create event ee3 on schedule at '2030-12-31 22:01:23' do set @a=5;
 show events;
-Db	Name	Definer	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
-second	ee1	root@localhost	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
-second	ee2	root@localhost	ONE TIME	2018-12-31 21:01:23	NULL	NULL	NULL	NULL	ENABLED
-second	ee3	root@localhost	ONE TIME	2030-12-31 22:01:23	NULL	NULL	NULL	NULL	ENABLED
+Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
+second	ee1	root@localhost	UTC	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
+second	ee2	root@localhost	UTC	ONE TIME	2018-12-31 21:01:23	NULL	NULL	NULL	NULL	ENABLED
+second	ee3	root@localhost	UTC	ONE TIME	2030-12-31 22:01:23	NULL	NULL	NULL	NULL	ENABLED
 drop database second;
 create database third;
 use third;
 show events;
-Db	Name	Definer	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
-third	ee1	root@localhost	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
-third	ee2	root@localhost	ONE TIME	2018-12-31 21:01:23	NULL	NULL	NULL	NULL	ENABLED
-third	ee3	root@localhost	ONE TIME	2030-12-31 22:01:23	NULL	NULL	NULL	NULL	ENABLED
+Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
+third	ee1	root@localhost	UTC	ONE TIME	2035-12-31 20:01:23	NULL	NULL	NULL	NULL	ENABLED
+third	ee2	root@localhost	UTC	ONE TIME	2018-12-31 21:01:23	NULL	NULL	NULL	NULL	ENABLED
+third	ee3	root@localhost	UTC	ONE TIME	2030-12-31 22:01:23	NULL	NULL	NULL	NULL	ENABLED
 drop database third;
 set time_zone = 'SYSTEM';
 use test;