An attempt to fix a sporadic valgrind memory leak in Event Scheduler:

streamline the event worker thread work flow and try to eliminate
possibilities for memory corruptions that might have been
lurking in previous (complicated) code.
This patch: 
 * removes Event_job_data::compile that was never used
 * cleans up Event_job_data::execute to minimize juggling with
   thread context and eliminate unneded code paths
 * Implements Security_context::change/restore_security_context
   to be able to re-use these methods in all stored programs
This is to maybe fix Bug#27733 "Valgrind failures in 
remove_table_from_cache".
Review comments applied.


sql/event_data_objects.cc:
  Remove Event_job_data::compile, which was never used without
  Event_job_data::execute().
  Merge the implementation of compile() with Event_job_data::execute().
  Reuse existing functions to prepare the event worker thread
  for execution instead of some previously copy-pasted code.
  Do not change and restore the current database inside 
  Event_job_data::execute(), just set the current database in the 
  thread, that is enough to parse and execute an event.
sql/event_data_objects.h:
  Update declarations.
sql/event_scheduler.cc:
  Allocate Event_job_data on stack.
sql/item_func.cc:
  Update to match the new declaration of restore_security_context()
sql/sp_head.cc:
  Update to match the new declaration of 
  change/restore_security_context()
sql/sql_class.cc:
  Move change/restore_security_context to class Security_context.
  Add more comments.
sql/sql_class.h:
  Make change/restore_security_context methods of Security_context.
  That allows us to reuse them in Event Scheduler (instead of a
  copy-paste presently used there).
sql/sql_trigger.cc:
  Update to match the new declaration of 
  change/restore_security_context()

1 files changed, 18 insertions, 36 deletions

diff --git a/sql/event_scheduler.cc b/sql/event_scheduler.cc
index 0603a299079..5844fecc227 100644
--- a/sql/event_scheduler.cc
+++ b/sql/event_scheduler.cc
@@ -277,8 +277,7 @@ Event_worker_thread::run(THD *thd, Event_queue_element_for_exec *event)
 {
   /* needs to be first for thread_stack */
   char my_stack;
-  int ret;
-  Event_job_data *job_data= NULL;
+  Event_job_data job_data;
   bool res;
 
   thd->thread_stack= &my_stack;                // remember where our stack is
@@ -291,60 +290,43 @@ Event_worker_thread::run(THD *thd, Event_queue_element_for_exec *event)
   if (res)
     goto end;
 
-  if (!(job_data= new Event_job_data()))
-    goto end;
-  else if ((ret= db_repository->
-                  load_named_event(thd, event->dbname, event->name, job_data)))
+  if ((res= db_repository->load_named_event(thd, event->dbname, event->name,
+                                            &job_data)))
   {
-    DBUG_PRINT("error", ("Got %d from load_named_event", ret));
+    DBUG_PRINT("error", ("Got error from load_named_event"));
     goto end;
   }
 
   sql_print_information("Event Scheduler: "
-                        "[%s.%s of %s] executing in thread %lu. ",
-                        job_data->dbname.str, job_data->name.str,
-                        job_data->definer.str, thd->thread_id);
+                        "[%s].[%s.%s] started in thread %lu.",
+                        job_data.definer.str,
+                        job_data.dbname.str, job_data.name.str,
+                        thd->thread_id);
 
   thd->enable_slow_log= TRUE;
 
-  ret= job_data->execute(thd, event->dropped);
+  res= job_data.execute(thd, event->dropped);
 
-  print_warnings(thd, job_data);
+  print_warnings(thd, &job_data);
 
-  switch (ret) {
-  case 0:
+  if (res)
+    sql_print_information("Event Scheduler: "
+                          "[%s].[%s.%s] event execution failed.",
+                          job_data.definer.str,
+                          job_data.dbname.str, job_data.name.str);
+  else
     sql_print_information("Event Scheduler: "
                           "[%s].[%s.%s] executed successfully in thread %lu.",
-                          job_data->definer.str,
-                          job_data->dbname.str, job_data->name.str,
+                          job_data.definer.str,
+                          job_data.dbname.str, job_data.name.str,
                           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;
-
   DBUG_PRINT("info", ("Done with Event %s.%s", event->dbname.str,
              event->name.str));
 
   delete event;
   deinit_event_thread(thd);
-  /*
-    Do not pthread_exit since we want local destructors for stack objects
-    to be invoked.
-  */
 }