A set of changes aiming to make the Event Scheduler more user-friendly

when there are no up-to-date system tables to support it:
 - initialize the scheduler before reporting "Ready for connections".
   This ensures that warnings, if any, are printed before "Ready for
   connections", and this message is not mangled.
 - do not abort the scheduler if there are no system tables
 - check the tables once at start up, remember the status and disable
   the scheduler if the tables are not up to date.
   If one attempts to use the scheduler with bad tables,
   issue an error message.
 - clean up the behaviour of the module under LOCK TABLES and pre-locking
   mode
 - make sure implicit commit of Events DDL works as expected.
 - add more tests


Collateral clean ups in the events code.

This patch fixes Bug#23631 Events: SHOW VARIABLES doesn't work 
when mysql.event is damaged


mysql-test/r/events.result:
  Update results.
mysql-test/r/events_bugs.result:
  Update results.
mysql-test/r/events_restart_phase1.result:
  Update results.
mysql-test/r/events_restart_phase2.result:
  Update results.
mysql-test/r/events_restart_phase3.result:
  Update results.
mysql-test/r/events_scheduling.result:
  Update results.
mysql-test/r/events_time_zone.result:
  Update results.
mysql-test/t/events.test:
  Add new tests for tampering with mysql.event and some more
  tests for sub-statements, LOCK TABLES mode and pre-locking.
mysql-test/t/events_bugs.test:
  Move the non-concurrent part of test for Bug 16420 to this file.
mysql-test/t/events_restart_phase1.test:
  Rewrite events_restart_* tests to take into account that now
  we check mysql.event table only once, at server startup.
mysql-test/t/events_restart_phase2.test:
  Rewrite events_restart_* tests to take into account that now
  we check mysql.event table only once, at server startup.
mysql-test/t/events_restart_phase3.test:
  Rewrite events_restart_* tests to take into account that now
  we check mysql.event table only once, at server startup.
mysql-test/t/events_scheduling.test:
  Add more coverage for event_scheduler global variable.
mysql-test/t/events_time_zone.test:
  Move the non-concurrent part of the tests for Bug 16420 to 
  events_bugs.test
sql/event_data_objects.cc:
  Move update_timing_fields functionality to Event_db_repository.
  Make loading of events from a table record more robust to tampering
  with the table - now we do not check mysql.event on every table open.
sql/event_data_objects.h:
  Cleanup.
sql/event_db_repository.cc:
  Now Event_db_repository is responsible for table I/O only.
  All the logic of events DDL is handled outside, in Events class please
  refer to the added test coverage to see how this change affected
  the behavior of Event Scheduler.
  Dependency on sp_head.h and sp.h removed.
  Make this module robust to tweaks with mysql.event table.
  Move check_system_tables from events.cc to this file
sql/event_db_repository.h:
  Cleanup declarations (remove unused ones, change return type to bool
  from int).
sql/event_queue.cc:
  Update to adapt to the new start up scheme of the Event Scheduler.
sql/event_queue.h:
  Cleanup declarations.
sql/event_scheduler.cc:
  Make all the error messages uniform:
  [SEVERITY] Event Scheduler: [user][schema.event] message
  Using append_identifier for error logging was an overkill - we may 
  need it only if the system character set may have NUL (null character)
  as part of a valid identifier, this is currently never the case, 
  whereas additional quoting did not look nice in the log.
sql/event_scheduler.h:
  Cleanup the headers.
sql/events.cc:
  Use a different start up procedure of Event Scheduler:
  - at start up, try to check the system tables first.
  If they are not up-to-date, disable the scheduler.
  - try to load all the active events. In case of a load error, abort
  start up.
  - do not parse an event on start up. Parsing only gives some information
  about event validity, but far not all.
  Consolidate the business logic of Events DDL in this module.
  Now opt_event_scheduler may change after start up and thus is protected
  by LOCK_event_metadata mutex.
sql/events.h:
  Use all-static-data-members approach to implement Singleton pattern.
sql/mysqld.cc:
  New invocation scheme of Events. Move some logic to events.cc.
  Initialize the scheduler before reporting "Ready for connections".
sql/set_var.cc:
  Clean up sys_var_thd_sql_mode::symbolic_mode_representation
  to work with a LEX_STRING.
  Move more logic related to @@events_scheduler global variable to Events
  module.
sql/set_var.h:
  Update declarations.
sql/share/errmsg.txt:
  If someone tampered with mysql.event table after the server has
  started we no longer give him/her a complete report what was actually 
  broken. Do not send the user to look at the error log in such case,
  as there is nothing there (check_table_intact is not executed).
sql/sp_head.cc:
  Update to a new declaration of 
  sys_var_thd_sql_mode::symbolic_mode_representation
sql/sql_db.cc:
  New invocation scheme of Events module.
sql/sql_parse.cc:
  Move more logic to Events module. Make sure that we are consistent
  in the way access rights are checked for Events DDL: always
  after committing the current transaction and checking the system tables.
sql/sql_show.cc:
  Update to the new declarations of 
  sys_var_thd_sql_mode::symbolic_mode_representation
sql/sql_test.cc:
  New invocation scheme of events.
sql/table.cc:
  mysql.event is a system table.
  Update check_table_intact to be concurrent, more verbose, and less smart.
sql/table.h:
  Add a helper method.
mysql-test/r/events_trans.result:
  New BitKeeper file ``mysql-test/r/events_trans.result''
mysql-test/t/events_trans.test:
  New BitKeeper file ``mysql-test/t/events_trans.test'':
  test cases for Event Scheduler that require a transactional
  storage engine.

1 files changed, 62 insertions, 44 deletions

diff --git a/sql/events.h b/sql/events.h
index f97a0c5f57e..db0e947ab6c 100644
--- a/sql/events.h
+++ b/sql/events.h
@@ -15,7 +15,11 @@
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
-class sp_name;
+/*
+  @file
+  A public interface of Events Scheduler module.
+*/
+
 class Event_parse_data;
 class Event_db_repository;
 class Event_queue;
@@ -40,6 +44,22 @@ sortcmp_lex_string(LEX_STRING s, LEX_STRING t, CHARSET_INFO *cs);
 /**
   @class Events -- a facade to the functionality of the Event Scheduler.
 
+  Every public operation against the scheduler has to be executed via the
+  interface provided by a static method of this class. No instance of this
+  class is ever created and it has no non-static data members.
+
+  The life cycle of the Events module is the following:
+
+  At server start up:
+     set_opt_event_scheduler() -> init_mutexes() -> init()
+  When the server is running:
+     create_event(), drop_event(), start_or_stop_event_scheduler(), etc
+  At shutdown:
+     deinit(), destroy_mutexes().
+
+  The peculiar initialization and shutdown cycle is an adaptation to the
+  outside server startup/shutdown framework and mimics the rest of MySQL
+  subsystems (ACL, time zone tables, etc).
 */
 
 class Events
@@ -53,47 +73,48 @@ public:
     EVENTS_DISABLED= 4
   };
 
-  static enum_opt_event_scheduler opt_event_scheduler;
-  static TYPELIB opt_typelib;
-  static TYPELIB var_typelib;
+  /* Possible values of @@event_scheduler variable */
+  static const TYPELIB var_typelib;
 
-  bool
-  init();
+  static bool
+  set_opt_event_scheduler(char *argument);
 
-  void
-  deinit();
+  static const char *
+  get_opt_event_scheduler_str();
 
-  void
-  init_mutexes();
+  /* A hack needed for Event_queue_element */
+  static Event_db_repository *
+  get_db_repository() { return db_repository; }
 
-  void
-  destroy_mutexes();
+  static bool
+  init(my_bool opt_noacl);
 
-  bool
-  start_execution_of_events();
+  static void
+  deinit();
 
-  bool
-  stop_execution_of_events();
+  static void
+  init_mutexes();
 
-  bool
-  is_execution_of_events_started();
+  static void
+  destroy_mutexes();
 
-  static Events *
-  get_instance();
+  static bool
+  start_or_stop_event_scheduler(enum enum_opt_event_scheduler start_or_stop);
 
-  bool
+  static bool
   create_event(THD *thd, Event_parse_data *parse_data, bool if_exists);
 
-  bool
-  update_event(THD *thd, Event_parse_data *parse_data, sp_name *rename_to);
+  static bool
+  update_event(THD *thd, Event_parse_data *parse_data,
+               LEX_STRING *new_dbname, LEX_STRING *new_name);
 
-  bool
+  static bool
   drop_event(THD *thd, LEX_STRING dbname, LEX_STRING name, bool if_exists);
 
-  void
+  static void
   drop_schema_events(THD *thd, char *db);
 
-  bool
+  static bool
   show_create_event(THD *thd, LEX_STRING dbname, LEX_STRING name);
 
   /* Needed for both SHOW CREATE EVENT and INFORMATION_SCHEMA */
@@ -104,31 +125,28 @@ public:
   static int
   fill_schema_events(THD *thd, TABLE_LIST *tables, COND * /* cond */);
 
-  void
+  static void
   dump_internal_status();
 
 private:
-  bool
-  check_system_tables(THD *thd);
+  static bool check_if_system_tables_error();
 
-  int
+  static bool
   load_events_from_db(THD *thd);
 
-  /* Singleton DP is used */
-  Events();
-  ~Events(){}
-
-  /* Singleton instance */
-  static Events singleton;
-
-  Event_queue         *event_queue;
-  Event_scheduler     *scheduler;
-  Event_db_repository *db_repository;
-
-  pthread_mutex_t LOCK_event_metadata;
-
-  bool check_system_tables_error;
+private:
+  /* Command line option names */
+  static const TYPELIB opt_typelib;
+  static pthread_mutex_t LOCK_event_metadata;
+  static Event_queue         *event_queue;
+  static Event_scheduler     *scheduler;
+  static Event_db_repository *db_repository;
+  /* Current state of Event Scheduler */
+  static enum enum_opt_event_scheduler opt_event_scheduler;
+  /* Set to TRUE if an error at start up */
+  static bool check_system_tables_error;
 
+private:
   /* Prevent use of these */
   Events(const Events &);
   void operator=(Events &);