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, 5 insertions, 2 deletions

diff --git a/mysql-test/r/events_bugs.result b/mysql-test/r/events_bugs.result
index a7f0594588d..1a34f098b12 100644
--- a/mysql-test/r/events_bugs.result
+++ b/mysql-test/r/events_bugs.result
@@ -25,9 +25,12 @@ ERROR HY000: Incorrect STARTS value: '99990101000000'
 create event e_55 on schedule every 10 minute ends 99990101000000 do drop table t;
 ERROR HY000: ENDS is either invalid or before STARTS
 create event e_55 on schedule at 10000101000000 do drop table t;
-ERROR HY000: Activation (AT) time is in the past
+ERROR HY000: Incorrect AT value: '10000101000000'
 create event e_55 on schedule at 20000101000000 do drop table t;
-ERROR HY000: Activation (AT) time is in the past
+Warnings:
+Note	1584	Event execution time is in the past and ON COMPLETION NOT PRESERVE is set. Event has not been created
+show events;
+Db	Name	Definer	Time zone	Type	Execute at	Interval value	Interval field	Starts	Ends	Status
 create event e_55 on schedule at 20200101000000 starts 10000101000000 do drop table t;
 ERROR 42000: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'starts 10000101000000 do drop table t' at line 1
 create event e_55 on schedule at 20200101000000 ends 10000101000000 do drop table t;