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

1 files changed, 39 insertions, 60 deletions

diff --git a/sql/event_scheduler.cc b/sql/event_scheduler.cc
index d50ea932596..a9a93cbc74b 100644
--- a/sql/event_scheduler.cc
+++ b/sql/event_scheduler.cc
@@ -37,7 +37,6 @@ extern pthread_attr_t connection_attrib;
 
 
 Event_db_repository *Event_worker_thread::db_repository;
-Events *Event_worker_thread::events_facade;
 
 
 static
@@ -80,11 +79,11 @@ Event_worker_thread::print_warnings(THD *thd, Event_job_data *et)
   prefix.length(0);
   prefix.append("Event Scheduler: [");
 
-  append_identifier(thd, &prefix, et->definer.str, et->definer.length);
+  prefix.append(et->definer.str, et->definer.length, system_charset_info);
   prefix.append("][", 2);
-  append_identifier(thd,&prefix, et->dbname.str, et->dbname.length);
+  prefix.append(et->dbname.str, et->dbname.length, system_charset_info);
   prefix.append('.');
-  append_identifier(thd,&prefix, et->name.str, et->name.length);
+  prefix.append(et->name.str, et->name.length, system_charset_info);
   prefix.append("] ", 2);
 
   List_iterator_fast<MYSQL_ERROR> it(thd->warn_list);
@@ -95,7 +94,6 @@ Event_worker_thread::print_warnings(THD *thd, Event_job_data *et)
     err_msg.length(0);
     err_msg.append(prefix);
     err_msg.append(err->msg, strlen(err->msg), system_charset_info);
-    err_msg.append("]");
     DBUG_ASSERT(err->level < 3);
     (sql_print_message_handlers[err->level])("%*s", err_msg.length(),
                                               err_msg.c_ptr());
@@ -239,7 +237,7 @@ event_scheduler_thread(void *arg)
 }
 
 
-/*
+/**
   Function that executes an event in a child thread. Setups the
   environment for the event execution and cleans after that.
 
@@ -266,7 +264,7 @@ event_worker_thread(void *arg)
 }
 
 
-/*
+/**
   Function that executes an event in a child thread. Setups the
   environment for the event execution and cleans after that.
 
@@ -315,17 +313,27 @@ Event_worker_thread::run(THD *thd, Event_queue_element_for_exec *event)
 
   print_warnings(thd, job_data);
 
-  sql_print_information("Event Scheduler: "
-                        "[%s.%s of %s] executed in thread %lu. "
-                        "RetCode=%d", job_data->dbname.str, job_data->name.str,
-                        job_data->definer.str, thd->thread_id, ret);
-  if (ret == EVEX_COMPILE_ERROR)
+  switch (ret) {
+  case 0:
     sql_print_information("Event Scheduler: "
-                          "COMPILE ERROR for event %s.%s of %s",
+                          "[%s].[%s.%s] executed successfully in thread %lu.",
+                          job_data->definer.str,
                           job_data->dbname.str, job_data->name.str,
-                          job_data->definer.str);
-  else if (ret == EVEX_MICROSECOND_UNSUP)
-    sql_print_information("Event Scheduler: MICROSECOND is not supported");
+                          thd->thread_id);
+    break;
+  case EVEX_COMPILE_ERROR:
+    sql_print_information("Event Scheduler: "
+                          "[%s].[%s.%s] event compilation failed.",
+                          job_data->definer.str,
+                          job_data->dbname.str, job_data->name.str);
+    break;
+  default:
+    sql_print_information("Event Scheduler: "
+                          "[%s].[%s.%s] event execution failed.",
+                          job_data->definer.str,
+                          job_data->dbname.str, job_data->name.str);
+    break;
+  }
 
 end:
   delete job_data;
@@ -349,66 +357,34 @@ end:
       problem. However, this comes at the price of introduction bi-directional
       association between class Events and class Event_worker_thread.
     */
-    events_facade->drop_event(thd, event->dbname, event->name, FALSE);
+    Events::drop_event(thd, event->dbname, event->name, FALSE);
   }
   DBUG_PRINT("info", ("Done with Event %s.%s", event->dbname.str,
              event->name.str));
 
   delete event;
   deinit_event_thread(thd);
-  pthread_exit(0);
-}
-
-
-/*
-  Performs initialization of the scheduler data, outside of the
-  threading primitives.
-
-  SYNOPSIS
-    Event_scheduler::init_scheduler()
-*/
-
-void
-Event_scheduler::init_scheduler(Event_queue *q)
-{
-  LOCK_DATA();
-  queue= q;
-  started_events= 0;
-  scheduler_thd= NULL;
-  state= INITIALIZED;
-  UNLOCK_DATA();
+  /*
+    Do not pthread_exit since we want local destructors for stack objects
+    to be invoked.
+  */
 }
 
 
-void
-Event_scheduler::deinit_scheduler() {}
-
-
-/*
-  Inits scheduler's threading primitives.
-
-  SYNOPSIS
-    Event_scheduler::init_mutexes()
-*/
-
-void
-Event_scheduler::init_mutexes()
+Event_scheduler::Event_scheduler(Event_queue *queue_arg)
+  :state(UNINITIALIZED),
+  scheduler_thd(NULL),
+  queue(queue_arg),
+  started_events(0)
 {
   pthread_mutex_init(&LOCK_scheduler_state, MY_MUTEX_INIT_FAST);
   pthread_cond_init(&COND_state, NULL);
 }
 
 
-/*
-  Deinits scheduler's threading primitives.
-
-  SYNOPSIS
-    Event_scheduler::deinit_mutexes()
-*/
-
-void
-Event_scheduler::deinit_mutexes()
+Event_scheduler::~Event_scheduler()
 {
+  stop();                                    /* does nothing if not running */
   pthread_mutex_destroy(&LOCK_scheduler_state);
   pthread_cond_destroy(&COND_state);
 }
@@ -639,6 +615,9 @@ Event_scheduler::is_running()
   Stops the scheduler (again). Waits for acknowledgement from the
   scheduler that it has stopped - synchronous stopping.
 
+  Already running events will not be stopped. If the user needs
+  them stopped manual intervention is needed.
+
   SYNOPSIS
     Event_scheduler::stop()