Allow mysql_upgrade to enable event after table is corrected

new features:
set event_scheduler=ON|OFF will now try to init event scheduler
if it's not enabled
set event_scheduler=default will try to enable it based on
the value of the event_scheduler when mysqld was started

client/mysql_upgrade.c

@@ -865,6 +865,7 @@ static const char *expected_errors[]=
   "ERROR 1060", /* Duplicate column name */
   "ERROR 1061", /* Duplicate key name */
   "ERROR 1054", /* Unknown column */
+  "ERROR 1290", /* RR_OPTION_PREVENTS_STATEMENT */
   0
 };
 

mysql-test/r/events_restart.result

@@ -18,7 +18,7 @@ change column body  body longtext character set utf8 collate utf8_bin;
 use events_test;
 select @@event_scheduler;
 @@event_scheduler
-DISABLED
+OFF
 show events;
 ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
 select event_name from information_schema.events;
@@ -40,12 +40,12 @@ ERROR HY000: Cannot proceed because system tables used by Event Scheduler were f
 drop event intact_check;
 ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
 set global event_scheduler=on;
-ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
+ERROR HY000: Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.
 set global event_scheduler=off;
-ERROR HY000: Cannot proceed because system tables used by Event Scheduler were found damaged at server start
+ERROR HY000: Event Scheduler: An error occurred when initializing system tables. Disabling the Event Scheduler.
 show variables like 'event_scheduler';
 Variable_name	Value
-event_scheduler	DISABLED
+event_scheduler	OFF
 Make sure that we still can create and drop databases,
 and no warnings are produced.
 drop database if exists mysqltest_database_not_exists;
@@ -58,6 +58,22 @@ Error	1545	Failed to open mysql.event
 Restore the original mysql.event table
 drop table mysql.event;
 rename table event_like to mysql.event;
+check that we can now enable events without restart
+set global event_scheduler=original;
+Warnings:
+Note	1408	Event Scheduler: Loaded 3 events
+select @@global.event_scheduler;
+@@global.event_scheduler
+ON
+set global event_scheduler=on;
+select @@global.event_scheduler;
+@@global.event_scheduler
+ON
+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	abc1	root@localhost	SYSTEM	RECURRING	#	1	SECOND	#	#	ENABLED	1	latin1	latin1_swedish_ci	latin1_swedish_ci
+events_test	abc2	root@localhost	SYSTEM	RECURRING	#	1	SECOND	#	#	ENABLED	1	latin1	latin1_swedish_ci	latin1_swedish_ci
+events_test	abc3	root@localhost	SYSTEM	RECURRING	#	1	SECOND	#	#	ENABLED	1	latin1	latin1_swedish_ci	latin1_swedish_ci
 Now let's restart the server again
 use events_test;
 select @@event_scheduler;

mysql-test/r/mysql_upgrade-6984.result

@@ -57,3 +57,4 @@ Phase 6/6: Running 'FLUSH PRIVILEGES'
 OK
 update mysql.user set password='' where user='root';
 flush privileges;
+set global event_scheduler=OFF;

mysql-test/r/skip_grants.result

@@ -59,7 +59,9 @@ DROP FUNCTION f1;
 DROP FUNCTION f2;
 DROP FUNCTION f3;
 set global event_scheduler=1;
-ERROR HY000: The MariaDB server is running with the --event-scheduler=DISABLED or --skip-grant-tables option so it cannot execute this statement
+Warnings:
+Note	1408	Event Scheduler: Loaded 0 events
+set global event_scheduler=0;
 select count(*) from information_schema.COLUMN_PRIVILEGES;
 count(*)
 0

mysql-test/t/events_restart.test

@@ -71,9 +71,9 @@ drop event intact_check_1;
 drop event intact_check_2;
 --error ER_EVENTS_DB_ERROR
 drop event intact_check;
---error ER_EVENTS_DB_ERROR
+--error ER_STARTUP
 set global event_scheduler=on;
---error ER_EVENTS_DB_ERROR
+--error ER_STARTUP
 set global event_scheduler=off;
 show variables like 'event_scheduler';
 --echo Make sure that we still can create and drop databases,
@@ -84,6 +84,16 @@ drop database mysqltest_db1;
 --echo Restore the original mysql.event table
 drop table mysql.event;
 rename table event_like to mysql.event;
+
+--echo check that we can now enable events without restart
+set global event_scheduler=original;
+select @@global.event_scheduler;
+set global event_scheduler=on;
+select @@global.event_scheduler;
+--sorted_result
+--replace_column 6 # 9 # 10 #
+show events;
+
 --echo Now let's restart the server again
 
 --source include/restart_mysqld.inc

mysql-test/t/mysql_upgrade-6984.test

@@ -19,4 +19,5 @@ connect(con1,localhost,root,foo,,,);
 
 update mysql.user set password='' where user='root';
 flush privileges;
-
+# Load event table
+set global event_scheduler=OFF;

mysql-test/t/skip_grants.test

@@ -112,8 +112,8 @@ DROP FUNCTION f3;
 #
 # Bug #26807 "set global event_scheduler=1" and --skip-grant-tables crashes server
 #
---error ER_OPTION_PREVENTS_STATEMENT
 set global event_scheduler=1;
+set global event_scheduler=0;
 
 #
 # Bug#26285 Selecting information_schema crahes server

scripts/mysql_system_tables_fix.sql

@@ -597,6 +597,8 @@ ALTER TABLE event ADD body_utf8 longblob DEFAULT NULL
                       AFTER db_collation;
 ALTER TABLE event MODIFY body_utf8 longblob DEFAULT NULL;
 
+# Enable event scheduler if the event table was not up to date before.
+set global event_scheduler=original;
 
 #
 # TRIGGER privilege

sql/events.h

@@ -79,9 +79,11 @@ class Events
     and the @@global.event_scheduler SQL variable.
     See sys_var.cc
   */
-  enum enum_opt_event_scheduler { EVENTS_OFF, EVENTS_ON, EVENTS_DISABLED };
+  enum enum_opt_event_scheduler { EVENTS_OFF, EVENTS_ON, EVENTS_DISABLED,
+                                  EVENTS_ORIGINAL };
   /* Protected using LOCK_global_system_variables only. */
-  static ulong opt_event_scheduler;
+  static ulong opt_event_scheduler, startup_state;
+  static ulong inited;
   static bool check_if_system_tables_error();
   static bool start(int *err_no);
   static bool stop();
@@ -91,8 +93,7 @@ class Events
   static Event_db_repository *
   get_db_repository() { return db_repository; }
 
-  static bool
-  init(bool opt_noacl);
+  static bool init(THD *thd, bool opt_noacl);
 
   static void
   deinit();
@@ -130,6 +131,11 @@ class Events
   static void
   dump_internal_status();
 
+  static void set_original_state(ulong startup_state_org)
+  {
+    startup_state= startup_state_org;
+  }
+
 private:
 
   static bool
@@ -139,8 +145,6 @@ class Events
   static Event_queue         *event_queue;
   static Event_scheduler     *scheduler;
   static Event_db_repository *db_repository;
-  /* Set to TRUE if an error at start up */
-  static bool check_system_tables_error;
 
 private:
   /* Prevent use of these */

sql/mysqld.cc

@@ -5507,7 +5507,15 @@ int mysqld_main(int argc, char **argv)
 
   execute_ddl_log_recovery();
 
-  if (Events::init(opt_noacl || opt_bootstrap))
+  /*
+    Change EVENTS_ORIGINAL to EVENTS_OFF (the default value) as there is no
+    point in using ORIGINAL during startup
+  */
+  if (Events::opt_event_scheduler == Events::EVENTS_ORIGINAL)
+    Events::opt_event_scheduler= Events::EVENTS_OFF;
+
+  Events::set_original_state(Events::opt_event_scheduler);
+  if (Events::init((THD*) 0, opt_noacl || opt_bootstrap))
     unireg_abort(1);
 
   if (opt_bootstrap)

sql/sql_error.cc

@@ -510,8 +510,10 @@ Diagnostics_area::set_error_status(uint sql_errno,
 void
 Diagnostics_area::disable_status()
 {
+  DBUG_ENTER("disable_status");
   DBUG_ASSERT(! is_set());
   m_status= DA_DISABLED;
+  DBUG_VOID_RETURN;
 }
 
 Warning_info::Warning_info(ulonglong warn_id_arg,

sql/sys_vars.cc

@@ -815,30 +815,26 @@ static Sys_var_ulong Sys_delayed_queue_size(
        VALID_RANGE(1, UINT_MAX), DEFAULT(DELAYED_QUEUE_SIZE), BLOCK_SIZE(1));
 
 #ifdef HAVE_EVENT_SCHEDULER
-static const char *event_scheduler_names[]= { "OFF", "ON", "DISABLED", NullS };
+static const char *event_scheduler_names[]= { "OFF", "ON", "DISABLED",
+                                              "ORIGINAL", NullS };
 static bool event_scheduler_check(sys_var *self, THD *thd, set_var *var)
 {
-  /* DISABLED is only accepted on the command line */
-  if (var->save_result.ulonglong_value == Events::EVENTS_DISABLED)
-    return true;
-  /*
-    If the scheduler was disabled because there are no/bad
-    system tables, produce a more meaningful error message
-    than ER_OPTION_PREVENTS_STATEMENT
-  */
-  if (Events::check_if_system_tables_error())
-    return true;
   if (Events::opt_event_scheduler == Events::EVENTS_DISABLED)
   {
     my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0),
              "--event-scheduler=DISABLED or --skip-grant-tables");
     return true;
   }
+  /* DISABLED is only accepted on the command line */
+  if (var->save_result.ulonglong_value == Events::EVENTS_DISABLED)
+    return true;
   return false;
 }
+
 static bool event_scheduler_update(sys_var *self, THD *thd, enum_var_type type)
 {
   int err_no= 0;
+  bool ret;
   uint opt_event_scheduler_value= Events::opt_event_scheduler;
   mysql_mutex_unlock(&LOCK_global_system_variables);
   /*
@@ -857,9 +853,25 @@ static bool event_scheduler_update(sys_var *self, THD *thd, enum_var_type type)
     rare and it's difficult to avoid it without opening up possibilities
     for deadlocks. See bug#51160.
   */
-  bool ret= opt_event_scheduler_value == Events::EVENTS_ON
-            ? Events::start(&err_no)
-            : Events::stop();
+
+  /* EVENTS_ORIGINAL means we should revert back to the startup state */
+  if (opt_event_scheduler_value == Events::EVENTS_ORIGINAL)
+  {
+    opt_event_scheduler_value= Events::opt_event_scheduler=
+      Events::startup_state;
+  }
+ 
+  /*
+    If the scheduler was not properly inited (because of wrong system tables),
+    try to init it again. This is needed for mysql_upgrade to work properly if
+    the event tables where upgraded.
+  */
+  if (!Events::inited && (Events::init(thd, 0) || !Events::inited))
+    ret= 1;
+  else
+    ret= opt_event_scheduler_value == Events::EVENTS_ON ?
+      Events::start(&err_no) :
+      Events::stop();
   mysql_mutex_lock(&LOCK_global_system_variables);
   if (ret)
   {