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

@@ -64,7 +64,7 @@ SHOW GRANTS;
 Grants for ev_test@localhost
 GRANT USAGE ON *.* TO 'ev_test'@'localhost'
 GRANT ALL PRIVILEGES ON `events_test`.* TO 'ev_test'@'localhost'
-GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE ON `events_test2`.* TO 'ev_test'@'localhost'
+GRANT SELECT, INSERT, UPDATE, DELETE, CREATE, DROP, REFERENCES, INDEX, ALTER, CREATE TEMPORARY TABLES, LOCK TABLES, EXECUTE, CREATE VIEW, SHOW VIEW, CREATE ROUTINE, ALTER ROUTINE, TRIGGER ON `events_test2`.* TO 'ev_test'@'localhost'
 "Here comes an error:";
 SHOW EVENTS;
 ERROR 42000: Access denied for user 'ev_test'@'localhost' to database 'events_test2'

mysql-test/r/events_stress.result

+CREATE DATABASE IF NOT EXISTS events_test;
+CREATE DATABASE events_test2;
+USE events_test2;
+CREATE EVENT ev_drop1 ON SCHEDULE EVERY 10 MINUTE DISABLE DO SELECT 1;
+CREATE EVENT ev_drop2 ON SCHEDULE EVERY 10 MINUTE DISABLE DO SELECT 1;
+CREATE EVENT ev_drop3 ON SCHEDULE EVERY 10 MINUTE DISABLE DO SELECT 1;
+USE events_test;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+COUNT(*)
+3
+DROP DATABASE events_test2;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+COUNT(*)
+0
+"Now testing stability - dropping db -> events while they are running"
+CREATE DATABASE events_test2;
+USE events_test2;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+COUNT(*)
+1000
+SET GLOBAL event_scheduler=1;
+DROP DATABASE events_test2;
+SET GLOBAL event_scheduler=0;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+COUNT(*)
+0
+CREATE DATABASE events_test3;
+USE events_test3;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test3';
+COUNT(*)
+950
+CREATE DATABASE events_test4;
+USE events_test4;
+CREATE DATABASE events_test2;
+USE events_test2;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+COUNT(*)
+1050
+DROP DATABASE events_test2;
+SET GLOBAL event_scheduler=0;
+DROP DATABASE events_test3;
+SET GLOBAL event_scheduler=1;
+DROP DATABASE events_test4;
+SET GLOBAL event_scheduler=1;
+USE events_test;
+DROP DATABASE events_test;

mysql-test/t/events.test

@@ -109,7 +109,6 @@ drop event one_event;
 
 
 
-
 create event e_26 on schedule at '2017-01-01 00:00:00' disable do set @a = 5;
 select db, name, body, definer, convert_tz(execute_at, 'UTC', 'SYSTEM'), on_completion from mysql.event;
 drop event e_26;

mysql-test/t/events_stress.test

+CREATE DATABASE IF NOT EXISTS events_test;
+#
+# DROP DATABASE test start (bug #16406)
+#
+CREATE DATABASE events_test2;
+USE events_test2;
+CREATE EVENT ev_drop1 ON SCHEDULE EVERY 10 MINUTE DISABLE DO SELECT 1;
+CREATE EVENT ev_drop2 ON SCHEDULE EVERY 10 MINUTE DISABLE DO SELECT 1;
+CREATE EVENT ev_drop3 ON SCHEDULE EVERY 10 MINUTE DISABLE DO SELECT 1;
+USE events_test;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+DROP DATABASE events_test2;
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+
+--echo "Now testing stability - dropping db -> events while they are running"
+CREATE DATABASE events_test2;
+USE events_test2;
+--disable_query_log
+let $1= 1000;
+while ($1)
+{
+  eval CREATE EVENT ev_drop$1 ON SCHEDULE EVERY 1 SECOND DO SELECT $1;
+  dec $1;
+}
+--enable_query_log
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+SET GLOBAL event_scheduler=1;
+--sleep 4
+DROP DATABASE events_test2;
+
+SET GLOBAL event_scheduler=0;
+--sleep 2
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+CREATE DATABASE events_test3;
+USE events_test3;
+--disable_query_log
+let $1= 950;
+while ($1)
+{
+  eval CREATE EVENT ev_drop$1 ON SCHEDULE EVERY 1 SECOND DO SELECT $1;
+  dec $1;
+}
+--enable_query_log
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test3';
+--sleep 3
+CREATE DATABASE events_test4;
+USE events_test4;
+--disable_query_log
+let $1= 860;
+while ($1)
+{
+  eval CREATE EVENT ev_drop$1 ON SCHEDULE EVERY 1 SECOND DO SELECT $1;
+  dec $1;
+}
+--enable_query_log
+
+
+CREATE DATABASE events_test2;
+USE events_test2;
+--disable_query_log
+let $1= 1050;
+while ($1)
+{
+  eval CREATE EVENT ev_drop$1 ON SCHEDULE EVERY 1 SECOND DO SELECT $1;
+  dec $1;
+}
+--enable_query_log
+SELECT COUNT(*) FROM INFORMATION_SCHEMA.EVENTS WHERE EVENT_SCHEMA='events_test2';
+--sleep 6
+DROP DATABASE events_test2;
+SET GLOBAL event_scheduler=0;
+DROP DATABASE events_test3;
+SET GLOBAL event_scheduler=1;
+DROP DATABASE events_test4;
+SET GLOBAL event_scheduler=1;
+USE events_test;
+#
+# DROP DATABASE test end (bug #16406)
+#
+DROP DATABASE events_test;

sql/event.cc

@@ -165,11 +165,34 @@ evex_open_event_table(THD *thd, enum thr_lock_type lock_type, TABLE **table)
 }
 
 
+
 /*
   Find row in open mysql.event table representing event
 
   SYNOPSIS
     evex_db_find_event_aux()
+      thd    Thread context
+      et     evet_timed object containing dbname, name & definer
+      table  TABLE object for open mysql.event table.
+
+  RETURN VALUE
+    0                  - Routine found
+    EVEX_KEY_NOT_FOUND - No routine with given name
+*/
+
+inline int
+evex_db_find_event_aux(THD *thd, event_timed *et, TABLE *table)
+{
+  return evex_db_find_event_by_name(thd, et->dbname, et->name,
+                                    et->definer, table);
+}
+
+
+/*
+  Find row in open mysql.event table representing event
+
+  SYNOPSIS
+    evex_db_find_event_by_name()
       thd    Thread context
       dbname Name of event's database
       rname  Name of the event inside the db  
@@ -181,13 +204,13 @@ evex_open_event_table(THD *thd, enum thr_lock_type lock_type, TABLE **table)
 */
 
 int
-evex_db_find_event_aux(THD *thd, const LEX_STRING dbname,
-                       const LEX_STRING ev_name,
-                       const LEX_STRING user_name,
-                       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)
 {
   byte key[MAX_KEY_LENGTH];
-  DBUG_ENTER("evex_db_find_event_aux");
+  DBUG_ENTER("evex_db_find_event_by_name");
   DBUG_PRINT("enter", ("name: %.*s", ev_name.length, ev_name.str));
 
   /*
@@ -373,7 +396,7 @@ db_create_event(THD *thd, event_timed *et, my_bool create_if_not,
   }
   
   DBUG_PRINT("info", ("check existance of an event with the same name"));
-  if (!evex_db_find_event_aux(thd, et->dbname, et->name, et->definer, table))
+  if (!evex_db_find_event_aux(thd, et, table))
   {
     if (create_if_not)
     {
@@ -511,7 +534,7 @@ db_update_event(THD *thd, event_timed *et, sp_name *new_name)
       goto err;    
     }
   
-    if (!evex_db_find_event_aux(thd, new_name->m_db, new_name->m_name,
+    if (!evex_db_find_event_by_name(thd, new_name->m_db, new_name->m_name,
                                 et->definer, table))
     {
       my_error(ER_EVENT_ALREADY_EXISTS, MYF(0), new_name->m_name.str);
@@ -524,8 +547,7 @@ db_update_event(THD *thd, event_timed *et, sp_name *new_name)
     overwrite the key and SE will tell us that it cannot find the already found
     row (copied into record[1] later
   */
-  if (EVEX_KEY_NOT_FOUND == evex_db_find_event_aux(thd, et->dbname, et->name,
-                                                   et->definer, table))
+  if (EVEX_KEY_NOT_FOUND == evex_db_find_event_aux(thd, et, table))
   {
     my_error(ER_EVENT_DOES_NOT_EXIST, MYF(0), et->name.str);
     goto err;    
@@ -603,8 +625,8 @@ db_find_event(THD *thd, sp_name *name, LEX_STRING definer, event_timed **ett,
     goto done;
   }
 
-  if ((ret= evex_db_find_event_aux(thd, name->m_db, name->m_name, definer,
-                                   table)))
+  if ((ret= evex_db_find_event_by_name(thd, name->m_db, name->m_name, definer,
+                                       table)))
   {
     my_error(ER_EVENT_DOES_NOT_EXIST, MYF(0), name->m_name.str);
     goto done;    
@@ -727,7 +749,7 @@ evex_remove_from_cache(LEX_STRING *db, LEX_STRING *name, bool use_lock,
     if (!sortcmp_lex_string(*name, et->name, system_charset_info) &&
         !sortcmp_lex_string(*db, et->dbname, system_charset_info))
     {
-      if (!et->is_running())
+      if (et->can_spawn_now())
       {
         DBUG_PRINT("evex_remove_from_cache", ("not running - free and delete"));
         et->free_sp();
@@ -887,7 +909,7 @@ evex_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
     goto done;
   }
 
-  if (!(ret= evex_db_find_event_aux(thd, et->dbname,et->name,et->definer,table)))
+  if (!(ret= evex_db_find_event_aux(thd, et, table)))
   {
     if ((ret= table->file->ha_delete_row(table->record[0])))
     { 	
@@ -923,3 +945,186 @@ evex_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
   DBUG_RETURN(ret);
 }
 
+
+/*
+  evex_drop_db_events - Drops all events in the selected database
+  
+  thd  - Thread
+  db   - ASCIIZ the name of the database
+  
+  Returns:
+    0  - OK
+    1  - Failed to delete a specific row
+    2  - Got NULL while reading db name from a row
+
+  Note:
+    The algo is the following
+    1. Go through the in-memory cache, if the scheduler is working
+       and for every event whose dbname matches the database we drop
+       check whether is currently in execution:
+       - event_timed::can_spawn() returns true -> the event is not
+         being executed in a child thread. The reason not to use
+         event_timed::is_running() is that the latter shows only if
+         it is being executed, which is 99% of the time in the thread
+         but there are some initiliazations before and after the
+         anonymous SP is being called. So if we delete in this moment
+         -=> *boom*, so we have to check whether the thread has been
+         spawned and can_spawn() is the right method.
+       - event_timed::can_spawn() returns false -> being runned ATM
+         just set the flags so it should drop itself.
+
+*/
+
+int
+evex_drop_db_events(THD *thd, char *db)
+{
+  TABLE *table;
+  READ_RECORD read_record_info;
+  MYSQL_LOCK *lock;
+  int ret= 0;
+  int i;
+  LEX_STRING db_lex= {db, strlen(db)};
+  
+  DBUG_ENTER("evex_drop_db_events");  
+  DBUG_PRINT("info",("dropping events from %s", db));
+
+
+  VOID(pthread_mutex_lock(&LOCK_event_arrays));
+
+  if ((ret= evex_open_event_table(thd, TL_WRITE, &table)))
+  {
+    sql_print_error("Table mysql.event is damaged.");
+    VOID(pthread_mutex_unlock(&LOCK_event_arrays));
+    DBUG_RETURN(SP_OPEN_TABLE_FAILED);
+  }
+
+  DBUG_PRINT("info",("%d elements in the queue",
+             evex_queue_num_elements(EVEX_EQ_NAME)));
+  VOID(pthread_mutex_lock(&LOCK_evex_running));
+  if (!evex_is_running)
+    goto skip_memory;
+
+  for (i= 0; i < evex_queue_num_elements(EVEX_EQ_NAME); ++i)
+  {
+    event_timed *et= evex_queue_element(&EVEX_EQ_NAME, i, event_timed*);
+    if (sortcmp_lex_string(et->dbname, db_lex, system_charset_info))
+      continue;
+
+    if (et->can_spawn_now_n_lock(thd))
+    {
+      DBUG_PRINT("info",("event %s not running - direct delete", et->name.str));
+      if (!(ret= evex_db_find_event_aux(thd, et, table)))
+      {
+        DBUG_PRINT("info",("event %s found on disk", et->name.str));
+        if ((ret= table->file->ha_delete_row(table->record[0])))
+        {
+          sql_print_error("Error while deleting a row - dropping "
+                          "a database. Skipping the rest.");
+          my_error(ER_EVENT_DROP_FAILED, MYF(0), et->name.str);
+          goto end;
+        }
+        DBUG_PRINT("info",("deleted event [%s] num [%d]. Time to free mem",
+                   et->name.str, i));
+      }
+      else if (ret == EVEX_KEY_NOT_FOUND)
+      {
+        sql_print_error("Expected to find event %s.%s of %s on disk-not there.",
+                         et->dbname.str, et->name.str, et->definer.str);
+      }
+      et->free_sp();
+      delete et;
+      et= 0;
+      /* no need to call et->spawn_unlock because we already cleaned et */
+    }
+    else
+    {
+      DBUG_PRINT("info",("event %s is running. setting exec_no_more and dropped",
+                  et->name.str));
+      et->flags|= EVENT_EXEC_NO_MORE;
+      et->dropped= TRUE;
+    }
+    DBUG_PRINT("info",("%d elements in the queue",
+               evex_queue_num_elements(EVEX_EQ_NAME)));
+    evex_queue_delete_element(&EVEX_EQ_NAME, i);// 1 is top
+    DBUG_PRINT("info",("%d elements in the queue",
+               evex_queue_num_elements(EVEX_EQ_NAME)));
+    /*
+      decrease so we start at the same position, there will be
+      less elements in the queue, it will still be ordered so on
+      next iteration it will be again i the current element or if
+      no more we finish.
+    */
+    --i;
+  }
+
+skip_memory:
+  /*
+   The reasoning behind having two loops is the following:
+   If there was only one loop, the table-scan, then for every element which
+   matches, the queue in memory has to be searched to remove the element.
+   While if we go first over the queue and remove what's in there we have only
+   one pass over it and after finishing it, moving to table-scan for the disabled
+   events. This needs quite less time and means quite less locking on
+   LOCK_event_arrays.
+  */
+  DBUG_PRINT("info",("Mem-cache checked, now going to db for disabled events"));
+  /* only enabled events are in memory, so we go now and delete the rest */
+  init_read_record(&read_record_info, thd, table ,NULL,1,0);
+  while (!(read_record_info.read_record(&read_record_info)) && !ret)
+  {
+    char *et_db;
+
+    if ((et_db= get_field(thd->mem_root, table->field[EVEX_FIELD_DB])) == NULL)
+    {
+      ret= 2;
+      break;
+    }
+    
+    LEX_STRING et_db_lex= {et_db, strlen(et_db)};
+    if (!sortcmp_lex_string(et_db_lex, db_lex, system_charset_info))
+    {
+      event_timed ett;
+      char *ptr;
+      
+      if ((ptr= get_field(thd->mem_root, table->field[EVEX_FIELD_STATUS]))
+           == NullS)
+      {
+        sql_print_error("Error while loading from mysql.event. "
+                        "Table probably corrupted");
+        goto end;
+      }
+      /*
+        When not running nothing is in memory so we have to clean
+        everything.
+        We don't delete EVENT_ENABLED events when the scheduler is running
+        because maybe this is an event which we asked to drop itself when
+        it is finished and it hasn't finished yet, so we don't touch it.
+        It will drop itself. The not running ENABLED events has been already
+        deleted from ha_delete_row() above in the loop over the QUEUE
+        (in case the executor is running).
+        'D' stands for DISABLED, 'E' for ENABLED - it's an enum
+      */
+      if ((evex_is_running && ptr[0] == 'D') || !evex_is_running)
+      {
+        DBUG_PRINT("info", ("Dropping %s.%s", et_db, ett.name.str));
+        if ((ret= table->file->ha_delete_row(table->record[0])))
+        {
+          my_error(ER_EVENT_DROP_FAILED, MYF(0), ett.name.str);
+          goto end;
+        }
+      }
+    }
+  }
+  DBUG_PRINT("info",("Disk checked for disabled events. Finishing."));
+
+end:
+  VOID(pthread_mutex_unlock(&LOCK_evex_running));
+  VOID(pthread_mutex_unlock(&LOCK_event_arrays));
+  end_read_record(&read_record_info);
+
+  thd->version--;  // Force close to free memory
+
+  close_thread_tables(thd);
+
+  DBUG_RETURN(ret);
+}

sql/event.h

@@ -79,6 +79,8 @@ class event_timed
 {
   event_timed(const event_timed &);	/* Prevent use of these */
   void operator=(event_timed &);
+  my_bool in_spawned_thread;
+  ulong locked_by_thread_id;
   my_bool running;
   pthread_mutex_t LOCK_running;
 
@@ -116,9 +118,10 @@ class event_timed
   bool free_sphead_on_delete;
   uint flags;//all kind of purposes
 
-  event_timed():running(0), status_changed(false), last_executed_changed(false),
-                expression(0), created(0), modified(0),
-                on_completion(MYSQL_EVENT_ON_COMPLETION_DROP),
+  event_timed():in_spawned_thread(0),locked_by_thread_id(0),
+                running(0), status_changed(false),
+                last_executed_changed(false), expression(0), created(0),
+                modified(0), on_completion(MYSQL_EVENT_ON_COMPLETION_DROP),
                 status(MYSQL_EVENT_ENABLED), sphead(0), dropped(false),
                 free_sphead_on_delete(true), flags(0)
                 
@@ -197,8 +200,45 @@ class event_timed
 
     return ret;  
   }
+
+  /*
+    Checks whether the object is being used in a spawned thread.
+    This method is for very basic checking. Use ::can_spawn_now_n_lock()
+    for most of the cases.
+  */
+
+  my_bool
+  can_spawn_now()
+  {
+    my_bool ret;
+    VOID(pthread_mutex_lock(&this->LOCK_running));
+    ret= !in_spawned_thread;
+    VOID(pthread_mutex_unlock(&this->LOCK_running));
+    return ret;  
+  }
+
+  /*
+    Checks whether this thread can lock the object for modification ->
+    preventing being spawned for execution, and locks if possible.
+    use ::can_spawn_now() only for basic checking because a race
+    condition may occur between the check and eventual modification (deletion)
+    of the object.
+  */
+
+  my_bool
+  can_spawn_now_n_lock(THD *thd);
+
+  int
+  spawn_unlock(THD *thd);
+
+  int
+  spawn_now(void * (*thread_func)(void*));
   
-  void free_sp()
+  void
+  spawn_thread_finish(THD *thd);
+  
+  void
+  free_sp()
   {
     delete sphead;
     sphead= 0;
@@ -221,7 +261,11 @@ evex_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
 int
 evex_open_event_table(THD *thd, enum thr_lock_type lock_type, TABLE **table);
 
-int sortcmp_lex_string(LEX_STRING s, LEX_STRING t, CHARSET_INFO *cs);
+int
+sortcmp_lex_string(LEX_STRING s, LEX_STRING t, CHARSET_INFO *cs);
+
+int
+evex_drop_db_events(THD *thd, char *db);
 
 int
 init_events();

sql/event_executor.cc

@@ -18,6 +18,11 @@
 #include "event.h"
 #include "sp.h"
 
+#define WAIT_STATUS_READY         0
+#define WAIT_STATUS_EMPTY_QUEUE   1
+#define WAIT_STATUS_NEW_TOP_EVENT 2
+#define WAIT_STATUS_STOP_EXECUTOR 3
+
 
 /* 
   Make this define DBUG_FAULTY_THR to be able to put breakpoints inside
@@ -165,18 +170,97 @@ init_event_thread(THD* thd)
   DBUG_RETURN(0);
 }
 
+
+/*
+  This function waits till the time next event in the queue should be 
+  executed.
+  
+  Returns
+    WAIT_STATUS_READY          There is an event to be executed right now
+    WAIT_STATUS_EMPTY_QUEUE    No events or the last event was dropped.
+    WAIT_STATUS_NEW_TOP_EVENT  New event has entered the queue and scheduled
+                               on top. Restart ticking.
+    WAIT_STATUS_STOP_EXECUTOR  The thread was killed or SET global event_scheduler=0;
+*/
+
+static int
+executor_wait_till_next_event_exec(THD *thd)
+{
+  event_timed *et;
+  TIME time_now;
+  int t2sleep;
+
+  DBUG_ENTER("executor_wait_till_next_event_exec");
+  /*
+    now let's see how much time to sleep, we know there is at least 1
+    element in the queue.
+  */
+  VOID(pthread_mutex_lock(&LOCK_event_arrays));
+  if (!evex_queue_num_elements(EVEX_EQ_NAME))
+  {
+    VOID(pthread_mutex_unlock(&LOCK_event_arrays));
+    DBUG_RETURN(1);
+  }
+  et= evex_queue_first_element(&EVEX_EQ_NAME, event_timed*);
+  DBUG_ASSERT(et);
+  if (et->status == MYSQL_EVENT_DISABLED)
+  {
+    DBUG_PRINT("evex main thread",("Now it is disabled-exec no more"));
+    if (et->dropped)
+      et->drop(thd);
+    delete et;
+    evex_queue_delete_element(&EVEX_EQ_NAME, 1);// 1 is top
+    VOID(pthread_mutex_unlock(&LOCK_event_arrays));
+    sql_print_information("Event found disabled, dropping.");
+    DBUG_RETURN(1);
+  }
+       
+  DBUG_PRINT("evex main thread",("computing time to sleep till next exec"));
+  // set the internal clock of thd
+  thd->end_time();
+  my_tz_UTC->gmt_sec_to_TIME(&time_now, thd->query_start());
+  t2sleep= evex_time_diff(&et->execute_at, &time_now);
+  VOID(pthread_mutex_unlock(&LOCK_event_arrays));
+
+  DBUG_PRINT("evex main thread",("unlocked LOCK_event_arrays"));
+  if (t2sleep > 0)
+  {
+    /*
+      We sleep t2sleep seconds but we check every second whether this thread
+      has been killed, or there is a new candidate
+    */
+    while (t2sleep-- && !thd->killed && event_executor_running_global_var &&
+           evex_queue_num_elements(EVEX_EQ_NAME) &&
+           (evex_queue_first_element(&EVEX_EQ_NAME, event_timed*) == et))
+    {
+      DBUG_PRINT("evex main thread",("will sleep a bit more"));
+      my_sleep(1000000);
+    }
+  }
+
+  int ret= 0;
+  if (!evex_queue_num_elements(EVEX_EQ_NAME))
+    ret= 1;
+  else if (evex_queue_first_element(&EVEX_EQ_NAME, event_timed*) != et)
+    ret= 2;
+  if (thd->killed && event_executor_running_global_var)
+    ret= 3;
+
+  DBUG_RETURN(ret);
+}
+
+
 pthread_handler_t
 event_executor_main(void *arg)
 {
   THD *thd;			/* needs to be first for thread_stack */
-  ulonglong iter_num= 0;
   uint i=0, j=0;
   my_ulonglong cnt= 0;
+  TIME time_now;
 
   DBUG_ENTER("event_executor_main");
   DBUG_PRINT("event_executor_main", ("EVEX thread started"));    
 
-
   // init memory root
   init_alloc_root(&evex_mem_root, MEM_ROOT_BLOCK_SIZE, MEM_ROOT_PREALLOC);
   
@@ -186,23 +270,24 @@ event_executor_main(void *arg)
 
   if (sizeof(my_time_t) != sizeof(time_t))
   {
-    sql_print_error("sizeof(my_time_t) != sizeof(time_t) ."
+    sql_print_error("SCHEDULER: sizeof(my_time_t) != sizeof(time_t) ."
                     "The scheduler will not work correctly. Stopping.");
+    DBUG_ASSERT(0);
     goto err_no_thd;
   }
   
   //TODO Andrey: Check for NULL
   if (!(thd = new THD)) // note that contructor of THD uses DBUG_ !
   {
-    sql_print_error("Cannot create THD for event_executor_main");
+    sql_print_error("SCHEDULER: Cannot create THD for the main thread.");
     goto err_no_thd;
   }
   thd->thread_stack = (char*)&thd; // remember where our stack is
   
   pthread_detach_this_thread();
-
+  
   if (init_event_thread(thd))
-    goto err;
+    goto finish;
   
   // make this thread invisible it has no vio -> show processlist won't see
   thd->system_thread= 1;
@@ -213,7 +298,7 @@ event_executor_main(void *arg)
   thread_running++;
   VOID(pthread_mutex_unlock(&LOCK_thread_count));
 
-  DBUG_PRINT("EVEX main thread", ("Initing events_queuey"));
+  DBUG_PRINT("EVEX main thread", ("Initing events_queue"));
 
   /*
     eventually manifest that we are running, not to crashe because of
@@ -229,15 +314,14 @@ event_executor_main(void *arg)
   thd->security_ctx->user= my_strdup("event_scheduler", MYF(0));
 
   if (evex_load_events_from_db(thd))
-    goto err;
+    goto finish;
 
   evex_main_thread_id= thd->thread_id;
 
-  sql_print_information("Scheduler thread started");
+  sql_print_information("SCHEDULER: Main thread started");
   while (!thd->killed)
   {
     TIME time_now;
-    my_time_t now;
     event_timed *et;
     
     cnt++;
@@ -246,7 +330,7 @@ event_executor_main(void *arg)
     thd->proc_info = "Sleeping";
     if (!event_executor_running_global_var)
     {
-      sql_print_information("Scheduler asked to stop.");
+      sql_print_information("SCHEDULER: Asked to stop.");
       break;
     }
 
@@ -255,62 +339,30 @@ event_executor_main(void *arg)
       my_sleep(1000000);// sleep 1s
       continue;
     }
-
-    {
-      int t2sleep;
-      /*
-        now let's see how much time to sleep, we know there is at least 1
-        element in the queue.
-      */
-      VOID(pthread_mutex_lock(&LOCK_event_arrays));
-      if (!evex_queue_num_elements(EVEX_EQ_NAME))
-      {
-        VOID(pthread_mutex_unlock(&LOCK_event_arrays));
-        continue;
-      }
-      et= evex_queue_first_element(&EVEX_EQ_NAME, event_timed*);
-      if (et->status == MYSQL_EVENT_DISABLED)
-      {
-        DBUG_PRINT("evex main thread",("Now it is disabled-exec no more"));
-        if (et->dropped)
-          et->drop(thd);
-        delete et;
-        evex_queue_delete_element(&EVEX_EQ_NAME, 1);// 1 is top
-        VOID(pthread_mutex_unlock(&LOCK_event_arrays));
-        sql_print_information("Event found disabled, dropping.");
-        continue;    
-      }
-        
-      DBUG_PRINT("evex main thread",("computing time to sleep till next exec"));
-      time((time_t *)&now);
-      my_tz_UTC->gmt_sec_to_TIME(&time_now, now);
-      t2sleep= evex_time_diff(&et->execute_at, &time_now);
-      VOID(pthread_mutex_unlock(&LOCK_event_arrays));
-
-      DBUG_PRINT("evex main thread",("unlocked LOCK_event_arrays"));
-      if (t2sleep > 0)
-      {
-        /*
-          We sleep t2sleep seconds but we check every second whether this thread
-          has been killed, or there is a new candidate
-        */
-        while (t2sleep-- && !thd->killed && event_executor_running_global_var &&
-               evex_queue_num_elements(EVEX_EQ_NAME) &&
-               (evex_queue_first_element(&EVEX_EQ_NAME, event_timed*) == et))
-        {
-          DBUG_PRINT("evex main thread",("will sleep a bit more"));
-          my_sleep(1000000);
-        }
-      }
-      if (!event_executor_running_global_var)
-      {
-        sql_print_information("Scheduler asked to stop.");
-        break;
-      }
+    
+restart_ticking:
+    switch (executor_wait_till_next_event_exec(thd)) {
+    case WAIT_STATUS_READY:                     // time to execute the event on top
+      DBUG_PRINT("evex main thread",("time to execute an event"));
+      break;
+    case WAIT_STATUS_EMPTY_QUEUE:               // no more events
+      DBUG_PRINT("evex main thread",("no more events"));
+      continue;
+      break;
+    case WAIT_STATUS_NEW_TOP_EVENT:            // new event on top in the queue
+      DBUG_PRINT("evex main thread",("restart ticking"));
+      goto restart_ticking;
+    case WAIT_STATUS_STOP_EXECUTOR:
+      sql_print_information("SCHEDULER: Asked to stop.");
+      goto finish;
+      break;
+    default:
+      DBUG_ASSERT(0);
     }
 
-
     VOID(pthread_mutex_lock(&LOCK_event_arrays));
+    thd->end_time();
+    my_tz_UTC->gmt_sec_to_TIME(&time_now, thd->query_start());
 
     if (!evex_queue_num_elements(EVEX_EQ_NAME))
     {
@@ -332,14 +384,13 @@ event_executor_main(void *arg)
     DBUG_PRINT("evex main thread",("it's right time"));
     if (et->status == MYSQL_EVENT_ENABLED)
     {
-      pthread_t th;
-
+      int fork_ret_code;
       DBUG_PRINT("evex main thread", ("[%10s] this exec at [%llu]", et->name.str,
                                TIME_to_ulonglong_datetime(&et->execute_at)));
       et->mark_last_executed(thd);
       if (et->compute_next_execution_time())
       {
-        sql_print_error("Error while computing time of %s.%s . "
+        sql_print_error("SCHEDULER: Error while computing time of %s.%s . "
                         "Disabling after execution.",
                         et->dbname.str, et->name.str);
         et->status= MYSQL_EVENT_DISABLED;
@@ -348,13 +399,23 @@ event_executor_main(void *arg)
                                TIME_to_ulonglong_datetime(&et->execute_at)));
 
       et->update_fields(thd);
-      ++iter_num;
-      DBUG_PRINT("info", ("  Spawning a thread %d", iter_num));
 #ifndef DBUG_FAULTY_THR
-      if (pthread_create(&th, NULL, event_executor_worker, (void*)et))
-      {
-        sql_print_error("Problem while trying to create a thread");
-        UNLOCK_MUTEX_AND_BAIL_OUT(LOCK_event_arrays, err);
+      thread_safe_increment(workers_count, &LOCK_workers_count);
+      switch ((fork_ret_code= et->spawn_now(event_executor_worker))) {
+      case EVENT_EXEC_CANT_FORK:
+        thread_safe_decrement(workers_count, &LOCK_workers_count);
+        sql_print_error("SCHEDULER: Problem while trying to create a thread");
+        UNLOCK_MUTEX_AND_BAIL_OUT(LOCK_event_arrays, finish);
+      case EVENT_EXEC_ALREADY_EXEC:
+        thread_safe_decrement(workers_count, &LOCK_workers_count);
+        sql_print_information("SCHEDULER: %s.%s in execution. Skip this time.",
+                              et->dbname.str, et->name.str);
+        break;
+      default:
+        DBUG_ASSERT(!fork_ret_code);
+        if (fork_ret_code)
+          thread_safe_decrement(workers_count, &LOCK_workers_count);
+        break;
       }
 #else
       event_executor_worker((void *) et);
@@ -364,22 +425,21 @@ event_executor_main(void *arg)
          et->flags |= EVENT_EXEC_NO_MORE;
 
       if ((et->flags & EVENT_EXEC_NO_MORE) || et->status == MYSQL_EVENT_DISABLED)
-        evex_queue_delete_element(&EVEX_EQ_NAME, 1);// 1 is top
+        evex_queue_delete_element(&EVEX_EQ_NAME, 0);// 0 is top, internally 1
       else
         evex_queue_first_updated(&EVEX_EQ_NAME);
     }
     DBUG_PRINT("evex main thread",("unlocking"));
     VOID(pthread_mutex_unlock(&LOCK_event_arrays));
   }// while
+finish:
 
-err:
   // First manifest that this thread does not work and then destroy
   VOID(pthread_mutex_lock(&LOCK_evex_running));
   evex_is_running= false;
   evex_main_thread_id= 0;
   VOID(pthread_mutex_unlock(&LOCK_evex_running));
 
-  sql_print_information("Event scheduler stopping. Waiting for worker threads to finish.");
 
   /*
     TODO: A better will be with a conditional variable
@@ -388,21 +448,33 @@ event_executor_main(void *arg)
     Read workers_count without lock, no need for locking.
     In the worst case we have to wait 1sec more.
   */
-  while (workers_count)
-    my_sleep(1000000);// 1s
+  sql_print_information("SCHEDULER: Stopping. Waiting for worker threads to finish.");
+  while (1)
+  {
+    VOID(pthread_mutex_lock(&LOCK_workers_count));
+    if (!workers_count)
+    {
+      VOID(pthread_mutex_unlock(&LOCK_workers_count));
+      break;
+    }
+    VOID(pthread_mutex_unlock(&LOCK_workers_count));
+    my_sleep(1000000);// 1s    
+  }
 
   /*
-    LEX_STRINGs reside in the memory root and will be destroyed with it.
-    Hence no need of delete but only freeing of SP
+    First we free all objects ...
+    Lock because a DROP DATABASE could be running in parallel and it locks on these
   */
-  // First we free all objects ...
+  sql_print_information("SCHEDULER: Emptying the queue.");
+  VOID(pthread_mutex_lock(&LOCK_event_arrays));
   for (i= 0; i < evex_queue_num_elements(EVEX_EQ_NAME); ++i)
   {
     event_timed *et= evex_queue_element(&EVEX_EQ_NAME, i, event_timed*);
     et->free_sp();
     delete et;
   }
-  // ... then we can thras the whole queue at once
+  VOID(pthread_mutex_unlock(&LOCK_event_arrays));
+  // ... then we can thrash the whole queue at once
   evex_queue_destroy(&EVEX_EQ_NAME);
   
   thd->proc_info = "Clearing";
@@ -426,7 +498,7 @@ event_executor_main(void *arg)
   VOID(pthread_mutex_unlock(&LOCK_evex_running));
 
   free_root(&evex_mem_root, MYF(0));
-  sql_print_information("Event scheduler stopped.");
+  sql_print_information("SCHEDULER: Stopped.");
 
 #ifndef DBUG_FAULTY_THR
   my_thread_end();
@@ -444,9 +516,6 @@ event_executor_worker(void *event_void)
   MEM_ROOT worker_mem_root;
 
   DBUG_ENTER("event_executor_worker");
-  VOID(pthread_mutex_lock(&LOCK_workers_count));
-  ++workers_count;  
-  VOID(pthread_mutex_unlock(&LOCK_workers_count));
 
   init_alloc_root(&worker_mem_root, MEM_ROOT_BLOCK_SIZE, MEM_ROOT_PREALLOC);
 
@@ -455,7 +524,7 @@ event_executor_worker(void *event_void)
 
   if (!(thd = new THD)) // note that contructor of THD uses DBUG_ !
   {
-    sql_print_error("Cannot create a THD structure in a scheduler worker thread");
+    sql_print_error("SCHEDULER: Cannot create a THD structure in an worker.");
     goto err_no_thd;
   }
   thd->thread_stack = (char*)&thd; // remember where our stack is
@@ -495,30 +564,23 @@ event_executor_worker(void *event_void)
     int ret;
     DBUG_PRINT("info", ("    EVEX EXECUTING event %s.%s [EXPR:%d]",
                event->dbname.str, event->name.str,(int) event->expression));
-    sql_print_information("    EVEX EXECUTING event %s.%s [EXPR:%d]",
+    sql_print_information("SCHEDULER: Executing event %s.%s [EXPR:%d]",
                event->dbname.str, event->name.str,(int) event->expression);
 
     ret= event->execute(thd, &worker_mem_root);
 
-    sql_print_information("    EVEX EXECUTED event %s.%s  [EXPR:%d]. RetCode=%d",
+    sql_print_information("SCHEDULER: Executed event %s.%s [EXPR:%d]. RetCode=%d",
                           event->dbname.str, event->name.str,
                           (int) event->expression, ret);
     if (ret == EVEX_COMPILE_ERROR)
-      sql_print_information("    EVEX COMPILE ERROR for event %s.%s",
+      sql_print_information("SCHEDULER:COMPILE ERROR for event %s.%s",
                              event->dbname.str, event->name.str);
     
     DBUG_PRINT("info", ("    EVEX EXECUTED event %s.%s  [EXPR:%d]. RetCode=%d",
                         event->dbname.str, event->name.str,
                         (int) event->expression, ret));
   }
-  if ((event->flags & EVENT_EXEC_NO_MORE) || event->status==MYSQL_EVENT_DISABLED)
-  {
-    DBUG_PRINT("event_executor_worker",
-               ("%s exec no more. to drop=%d",event->name.str, event->dropped));
-    if (event->dropped)
-      event->drop(thd);
-    delete event;
-  }
+  event->spawn_thread_finish(thd);
 
   thd->db= 0;
 
@@ -548,10 +610,7 @@ event_executor_worker(void *event_void)
 err_no_thd:
 
   free_root(&worker_mem_root, MYF(0));
-  
-  VOID(pthread_mutex_lock(&LOCK_workers_count));
-  --workers_count;  
-  VOID(pthread_mutex_unlock(&LOCK_workers_count));
+  thread_safe_decrement(workers_count, &LOCK_workers_count);
 
 #ifndef DBUG_FAULTY_THR
   my_thread_end();
@@ -574,7 +633,7 @@ evex_load_events_from_db(THD *thd)
 
   if ((ret= evex_open_event_table(thd, TL_READ, &table)))
   {
-    sql_print_error("Table mysql.event is damaged.");
+    sql_print_error("SCHEDULER: Table mysql.event is damaged. Can not open.");
     DBUG_RETURN(SP_OPEN_TABLE_FAILED);
   }
 
@@ -594,7 +653,7 @@ evex_load_events_from_db(THD *thd)
     
     if ((ret= et->load_from_row(&evex_mem_root, table)))
     {
-      sql_print_error("Error while loading from mysql.event. "
+      sql_print_error("SCHEDULER: Error while loading from mysql.event. "
                       "Table probably corrupted");
       goto end;
     }
@@ -606,11 +665,11 @@ evex_load_events_from_db(THD *thd)
     }
     
     DBUG_PRINT("evex_load_events_from_db",
-            ("Event %s loaded from row. Time to compile", et->name.str));
+              ("Event %s loaded from row. Time to compile", et->name.str));
     
     if ((ret= et->compile(thd, &evex_mem_root)))
     {
-      sql_print_error("Error while compiling %s.%s. Aborting load.",
+      sql_print_error("SCHEDULER: Error while compiling %s.%s. Aborting load.",
                       et->dbname.str, et->name.str);
       goto end;
     }
@@ -618,8 +677,8 @@ evex_load_events_from_db(THD *thd)
     // let's find when to be executed  
     if (et->compute_next_execution_time())
     {
-      sql_print_error("Error while computing execution time of %s.%s. Skipping",
-                       et->dbname.str, et->name.str);
+      sql_print_error("SCHEDULER: Error while computing execution time of %s.%s."
+                      " Skipping", et->dbname.str, et->name.str);
       continue;
     }
     
@@ -640,7 +699,7 @@ evex_load_events_from_db(THD *thd)
   thd->version--;  // Force close to free memory
 
   close_thread_tables(thd);
-  sql_print_information("Scheduler loaded %d event%s", count, (count == 1)?"":"s");
+  sql_print_information("SCHEDULER: Loaded %d event%s", count, (count == 1)?"":"s");
   DBUG_PRINT("info", ("Status code %d. Loaded %d event(s)", ret, count));
 
   DBUG_RETURN(ret);

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);

sql/event_timed.cc

@@ -879,11 +879,12 @@ event_timed::drop(THD *thd)
   TABLE *table;
   int ret= 0;
   DBUG_ENTER("event_timed::drop");
+  DBUG_PRINT("info",("%s.%s", dbname.str, name.str));
 
   if (evex_open_event_table(thd, TL_WRITE, &table))
     DBUG_RETURN(-1);
 
-  if (evex_db_find_event_aux(thd, dbname, name, definer, table))
+  if (evex_db_find_event_by_name(thd, dbname, name, definer, table))
     DBUG_RETURN(-2);
 
   if ((ret= table->file->ha_delete_row(table->record[0])))
@@ -919,7 +920,7 @@ event_timed::update_fields(THD *thd)
   }
 
 
-  if ((ret= evex_db_find_event_aux(thd, dbname, name, definer, table)))
+  if ((ret= evex_db_find_event_by_name(thd, dbname, name, definer, table)))
     goto done;
 
   store_record(table,record[1]);
@@ -1059,6 +1060,7 @@ event_timed::compile(THD *thd, MEM_ROOT *mem_root)
   MEM_ROOT *tmp_mem_root= 0;
   LEX *old_lex= thd->lex, lex;
   char *old_db;
+  int old_db_length;
   event_timed *ett;
   sp_name *spn;
   char *old_query;
@@ -1088,7 +1090,9 @@ event_timed::compile(THD *thd, MEM_ROOT *mem_root)
   old_query_len= thd->query_length;
   old_query= thd->query;
   old_db= thd->db;
+  old_db_length= thd->db_length;
   thd->db= dbname.str;
+  thd->db_length= dbname.length;
   thd->query= get_show_create_event(thd, &thd->query_length);
   DBUG_PRINT("event_timed::compile", ("query:%s",thd->query));
 
@@ -1148,3 +1152,135 @@ event_timed::compile(THD *thd, MEM_ROOT *mem_root)
   DBUG_RETURN(ret);
 }
 
+
+/*
+  Checks whether this thread can lock the object for modification ->
+  preventing being spawned for execution, and locks if possible.
+  use ::can_spawn_now() only for basic checking because a race
+  condition may occur between the check and eventual modification (deletion)
+  of the object.
+
+  Returns
+    true  - locked
+    false - cannot lock
+*/
+
+my_bool
+event_timed::can_spawn_now_n_lock(THD *thd)
+{
+  my_bool ret= FALSE;
+  VOID(pthread_mutex_lock(&this->LOCK_running));
+  if (!in_spawned_thread)
+  {
+    in_spawned_thread= TRUE;
+    ret= TRUE;
+    locked_by_thread_id= thd->thread_id;
+  }
+  VOID(pthread_mutex_unlock(&this->LOCK_running));
+  return ret;  
+}
+
+
+extern pthread_attr_t connection_attrib;
+
+/*
+  Checks whether is possible and forks a thread. Passes self as argument.
+  
+  Returns
+  EVENT_EXEC_STARTED       - OK
+  EVENT_EXEC_ALREADY_EXEC  - Thread not forked, already working
+  EVENT_EXEC_CANT_FORK     - Unable to spawn thread (error)
+*/
+
+int
+event_timed::spawn_now(void * (*thread_func)(void*))
+{  
+  int ret= EVENT_EXEC_STARTED;
+  static uint exec_num= 0;
+  DBUG_ENTER("event_timed::spawn_now");
+  DBUG_PRINT("info", ("[%s.%s]", dbname.str, name.str));
+
+  VOID(pthread_mutex_lock(&this->LOCK_running));
+  if (!in_spawned_thread)
+  {
+    pthread_t th;
+    in_spawned_thread= true;
+    if (pthread_create(&th, &connection_attrib, thread_func, (void*)this))
+    {
+      DBUG_PRINT("info", ("problem while spawning thread"));
+      ret= EVENT_EXEC_CANT_FORK;
+      in_spawned_thread= false;
+    }
+#ifndef DBUG_OFF
+    else
+    {
+      sql_print_information("SCHEDULER: Started thread %d", ++exec_num);
+      DBUG_PRINT("info", ("thread spawned"));
+    }
+#endif
+  }
+  else
+  {
+    DBUG_PRINT("info", ("already in spawned thread. skipping"));
+    ret= EVENT_EXEC_ALREADY_EXEC;
+  }
+  VOID(pthread_mutex_unlock(&this->LOCK_running));
+
+  DBUG_RETURN(ret);  
+}
+
+
+void
+event_timed::spawn_thread_finish(THD *thd)
+{
+  DBUG_ENTER("event_timed::spawn_thread_finish");
+  VOID(pthread_mutex_lock(&this->LOCK_running));
+  in_spawned_thread= false;
+  if ((flags & EVENT_EXEC_NO_MORE) || status == MYSQL_EVENT_DISABLED)
+  {
+    DBUG_PRINT("info", ("%s exec no more. to drop=%d", name.str, dropped));
+    if (dropped)
+      drop(thd);
+    VOID(pthread_mutex_unlock(&this->LOCK_running));
+    delete this;
+    DBUG_VOID_RETURN;
+  }
+  VOID(pthread_mutex_unlock(&this->LOCK_running));
+  DBUG_VOID_RETURN;
+}
+
+
+/*
+  Unlocks the object after it has been locked with ::can_spawn_now_n_lock()
+
+  Returns
+    0 - ok
+    1 - not locked by this thread
+  
+*/
+ 
+
+int
+event_timed::spawn_unlock(THD *thd)
+{
+  int ret= 0;
+  VOID(pthread_mutex_lock(&this->LOCK_running));
+  if (!in_spawned_thread)
+  {
+    if (locked_by_thread_id == thd->thread_id)
+    {        
+      in_spawned_thread= FALSE;
+      locked_by_thread_id= 0;
+    }
+    else
+    {
+      sql_print_error("A thread tries to unlock when he hasn't locked. "
+                      "thread_id=%ld locked by %ld",
+                      thd->thread_id, locked_by_thread_id);
+      DBUG_ASSERT(0);
+      ret= 1;
+    }
+  }
+  VOID(pthread_mutex_unlock(&this->LOCK_running));
+  return ret;  
+}

sql/sql_db.cc

@@ -20,6 +20,7 @@
 #include "mysql_priv.h"
 #include <mysys_err.h>
 #include "sp.h"
+#include "event.h"
 #include <my_dir.h>
 #include <m_ctype.h>
 #ifdef __WIN__
@@ -748,6 +749,7 @@ bool mysql_rm_db(THD *thd,char *db,bool if_exists, bool silent)
 
 exit:
   (void)sp_drop_db_routines(thd, db); /* QQ Ignore errors for now  */
+  (void)evex_drop_db_events(thd, db); /* QQ Ignore errors for now  */
   start_waiting_global_read_lock(thd);
   /*
     If this database was the client's selected database, we silently change the