fix for bug#16406 (Events: DROP DATABASE doesn't automatically drop events)

WL#1034
- This changeset also changes the executor so its quite more stable now.
  Stressing test case added that executes ~800 events per second and dropping
  hundreds of events at once using DROP DATABASE.
(with fixes after review of JimW)
(with fixes after review of Serg)


mysql-test/r/events.result:
  update results after TRIGGER_ACL was added
mysql-test/t/events.test:
  -redundant line
sql/event.cc:
  Implemented evex_db_drop_events() which drops all events
  from a specific database. Needed for SQLCOM_DROP_DATABASE
sql/event.h:
  - protect the event better (see the changes to event_executor.cc
    and event.cc). An event object could be used in a spawned thread
    before it's executed but till now the object is marked as being
    executed when the anonymous sp_head is executed. However, there are
    timeframes before and after that during which the event is not marked
    as executed and other thread may delete the object -> so we end with
    a nirvana pointer.
sql/event_executor.cc:
  - extract some of the code executed in the main thread to a function. Too long
    functions are bad for the overview.
  - prepend all information/error messages to the console with "SCHEDULER:" for
    better overview, and easied searching in the log tables.
sql/event_priv.h:
  - change the name, of evex_db_find_event_by_name() and don't
    used C++ features like function overloading
  - define consts for result returned from event_timed::spawn_now()
sql/event_timed.cc:
  - add few methods related to event execution.
    now the event spawns the worker thread and
    passes itself as parameter. This way it locks itself for exectution
    first and then spawning -> no race condition. When the worker thread
    has finished working with the reference it calls back
    event_timed::spawn_thread_finish() to unlock itself.
sql/sql_db.cc:
  - call evex_drop_db_events() on DROP DATABASE

1 files changed, 8 insertions, 4 deletions

diff --git a/sql/event_priv.h b/sql/event_priv.h
index 7d1cdbcd264..7bcb26aaed0 100644
--- a/sql/event_priv.h
+++ b/sql/event_priv.h
@@ -19,6 +19,10 @@
 #include "mysql_priv.h"
 
 
+#define EVENT_EXEC_STARTED      0
+#define EVENT_EXEC_ALREADY_EXEC 1
+#define EVENT_EXEC_CANT_FORK    2
+
 #define EVEX_USE_QUEUE
 
 #define UNLOCK_MUTEX_AND_BAIL_OUT(__mutex, __label) \
@@ -32,10 +36,10 @@ int
 my_time_compare(TIME *a, TIME *b);
 
 int
-evex_db_find_event_aux(THD *thd, const LEX_STRING dbname,
-                       const LEX_STRING rname,
-                       const LEX_STRING definer,
-                       TABLE *table);
+evex_db_find_event_by_name(THD *thd, const LEX_STRING dbname,
+                          const LEX_STRING ev_name,
+                          const LEX_STRING user_name,
+                          TABLE *table);
                        
 int 
 event_timed_compare_q(void *vptr, byte* a, byte *b);