- fix for bug #16414 (Events: Crash or hang if event drops itself)

WL#1034 (Internal CRON)
(with post-review fix)


mysql-test/r/events.result:
  update the result
mysql-test/t/events.test:
  use --sleep instead of select sleep()
  enable some scheduler related tests. They were disabled because of a hang that
  happened. The hang is fixed with this bugfix.
sql/event.cc:
  - evex_remove_from_cache reports back whether the in_memory
    object was deleted or was scheduled. In case scheduling then
    don't delete it from outside but let it do it itself
  - move out db interaction code out of evex_drop_event to db_drop_event
    so it can be called from outter space :)
sql/event_priv.h:
  - export the new function db_drop_event()
sql/event_timed.cc:
  - use db_drop_event() and don't implement the dropping ourselves
sql/sql_parse.cc:
  - some debug info about the status code returned.

mysql-test/r/events.result

@@ -15,20 +15,11 @@ create event event2 on schedule every 2 second starts now() ends date_add(now(),
 drop event event2;
 create event e_43 on schedule every 1 second do set @a = 5;
 set global event_scheduler = 1;
-select sleep(2);
-sleep(2)
-0
 alter event e_43 do alter event e_43 do set @a = 4;
-select sleep(3);
-sleep(3)
-0
 select db, name, body, status, interval_field, interval_value from mysql.event;
 db	name	body	status	interval_field	interval_value
 events_test	e_43	 set @a = 4	ENABLED	SECOND	1
 drop event e_43;
-select sleep(1);
-sleep(1)
-0
 set global event_scheduler = 0;
 create table t_event3 (a int, b float);
 drop event if exists event3;
@@ -121,6 +112,7 @@ drop event two_event;
 drop event three_event;
 drop user ev_test@localhost;
 drop event one_event;
+"Sleep a bit so the server closes the second connection"
 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;
 db	name	body	definer	convert_tz(execute_at, 'UTC', 'SYSTEM')	on_completion
@@ -137,4 +129,70 @@ set event_scheduler=0;
 ERROR HY000: Variable 'event_scheduler' is a GLOBAL variable and should be set with SET GLOBAL
 set global event_scheduler=2;
 ERROR 42000: Variable 'event_scheduler' can't be set to the value of '2'
+"DISABLE the scheduler. Testing that it does not work when the variable is 0"
+set global event_scheduler=0;
+select definer, name, db from mysql.event;
+definer	name	db
+select get_lock("test_lock1", 20);
+get_lock("test_lock1", 20)
+1
+create event закачка on schedule every 10 hour do select get_lock("test_lock1", 20);
+"Should return 1 row"
+select definer, name, db from mysql.event;
+definer	name	db
+root@localhost	закачка	events_test
+"Should be only 1 process"
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+#	root	localhost	events_test	Query	#	NULL	show processlist
+select release_lock("test_lock1");
+release_lock("test_lock1")
+1
+drop event закачка;
+"Should have 0 events"
+select count(*) from mysql.event;
+count(*)
+0
+"ENABLE the scheduler and get a lock"
+set global event_scheduler=1;
+select get_lock("test_lock2", 20);
+get_lock("test_lock2", 20)
+1
+"Create an event which tries to acquire a mutex. The event locks on the mutex"
+create event закачка on schedule every 10 hour do select get_lock("test_lock2", 20);
+"Let some time pass to the event starts"
+"Should have only 3 processes: the scheduler, our conn and the locked event"
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+#	root	localhost	events_test	Query	#	NULL	show processlist
+#	event_scheduler		NULL	Connect	#	Sleeping	NULL
+#	root		events_test	Connect	#	User lock	select get_lock("test_lock2", 20)
+"Release the mutex, the event worker should finish."
+select release_lock("test_lock2");
+release_lock("test_lock2")
+1
+drop event закачка;
+set global event_scheduler=1;
+select get_lock("test_lock2_1", 20);
+get_lock("test_lock2_1", 20)
+1
+create event закачка21 on schedule every 10 hour do select get_lock("test_lock2_1", 20);
+"Should see 2 processes, one locked on get_lock("
+"Shutting down the scheduler, it should wait for the running event"
+set global event_scheduler=0;
+"Should have only 3 processes: the scheduler, our conn and the locked event"
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+#	root	localhost	events_test	Query	#	NULL	show processlist
+#	event_scheduler		NULL	Connect	#	Sleeping	NULL
+#	root		events_test	Connect	#	User lock	select get_lock("test_lock2_1", 20)
+"Release the lock so the child process should finish. Hence the scheduler also"
+select release_lock("test_lock2_1");
+release_lock("test_lock2_1")
+1
+"Should have only our process now:"
+show processlist;
+Id	User	Host	db	Command	Time	State	Info
+#	root	localhost	events_test	Query	#	NULL	show processlist
+drop event закачка21;
 drop database events_test;

mysql-test/t/events.test

@@ -17,12 +17,12 @@ drop event event2;
 
 create event e_43 on schedule every 1 second do set @a = 5;
 set global event_scheduler = 1;
-select sleep(2);
+--sleep 2
 alter event e_43 do alter event e_43 do set @a = 4;
-select sleep(3);
+--sleep 2
 select db, name, body, status, interval_field, interval_value from mysql.event;
 drop event e_43;
-select sleep(1);
+--sleep 1
 set global event_scheduler = 0;
 
 create table t_event3 (a int, b float);
@@ -107,8 +107,8 @@ drop event one_event;
 ##INFORMATION_SCHEMA.EVENTS test end
 #
 
-
-
+--echo "Sleep a bit so the server closes the second connection"
+--sleep 2
 
 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;
@@ -129,23 +129,38 @@ set event_scheduler=0;
 --error 1231
 set global event_scheduler=2;
 
-#set global event_scheduler=0;
-#select count(*) from mysql.event;
-#select get_lock("test_lock1", 20);
-#create event закачка on schedule every 10 hour do select get_lock("test_lock1", 20);
-#select count(*) from mysql.event;
-##show processlist;
-#select release_lock("test_lock1");
-#drop event закачка;
-#select count(*) from mysql.event;
+--echo "DISABLE the scheduler. Testing that it does not work when the variable is 0"
+set global event_scheduler=0;
+select definer, name, db from mysql.event;
+select get_lock("test_lock1", 20);
+create event закачка on schedule every 10 hour do select get_lock("test_lock1", 20);
+--echo "Should return 1 row"
+select definer, name, db from mysql.event;
+
+--echo "Should be only 1 process"
+--replace_column 1 # 6 #
+show processlist;
+select release_lock("test_lock1");
+drop event закачка;
+--echo "Should have 0 events"
+select count(*) from mysql.event;
+
 #
-#set global event_scheduler=1;
-#select get_lock("test_lock2", 20);
-#create event закачка on schedule every 10 hour do select get_lock("test_lock2", 20);
-#select sleep(2);
-#show processlist;
-#select release_lock("test_lock2");
-#drop event закачка;
+#
+#
+--echo "ENABLE the scheduler and get a lock"
+set global event_scheduler=1;
+select get_lock("test_lock2", 20);
+--echo "Create an event which tries to acquire a mutex. The event locks on the mutex"
+create event закачка on schedule every 10 hour do select get_lock("test_lock2", 20);
+--echo "Let some time pass to the event starts"
+--sleep 2
+--echo "Should have only 3 processes: the scheduler, our conn and the locked event"
+--replace_column 1 # 6 #
+show processlist;
+--echo "Release the mutex, the event worker should finish."
+select release_lock("test_lock2");
+drop event закачка;
 
 ##
 ## 1. get a lock
@@ -155,26 +170,33 @@ set global event_scheduler=2;
 ## 5. kill the scheduler, it will wait for the child to stop
 ## 6. both processes should be there on show processlist
 ## 7. release the lock and sleep, both scheduler and child should end
-#set global event_scheduler=1;
-#select get_lock("test_lock2_1", 20);
-#create event закачка21 on schedule every 10 hour do select get_lock("test_lock2_1", 20);
-#select sleep(2);
-##show processlist;
-#set global event_scheduler=0;
-#select sleep(2);
-##show processlist;
-#select release_lock("test_lock2_1");
-#select sleep(2);
-##show processlist;
-#drop event закачка21;
-
-#set global event_scheduler=1;
-#select get_lock("test_lock3", 20);
-#create event закачка on schedule every 10 hour do select get_lock("test_lock3", 20);
-#select sleep(2);
+set global event_scheduler=1;
+select get_lock("test_lock2_1", 20);
+create event закачка21 on schedule every 10 hour do select get_lock("test_lock2_1", 20);
+--sleep 1
+--echo "Should see 2 processes, one locked on get_lock("
 #show processlist;
-#drop event закачка;
-#select release_lock("test_lock3");
+--echo "Shutting down the scheduler, it should wait for the running event"
+set global event_scheduler=0;
+--sleep 1
+--echo "Should have only 3 processes: the scheduler, our conn and the locked event"
+--replace_column 1 # 6 #
+show processlist;
+--echo "Release the lock so the child process should finish. Hence the scheduler also"
+select release_lock("test_lock2_1");
+--sleep 1
+--echo "Should have only our process now:"
+--replace_column 1 # 6 #
+show processlist;
+drop event закачка21;
+
+##set global event_scheduler=1;
+##select get_lock("test_lock3", 20);
+##create event закачка on schedule every 10 hour do select get_lock("test_lock3", 20);
+##select sleep(2);
+##show processlist;
+##drop event закачка;
+##select release_lock("test_lock3");
 
 #
 # test with very often occuring event
@@ -182,14 +204,15 @@ set global event_scheduler=2;
 ##select get_lock("test_lock4", 20);
 ##create event закачка4 on schedule every 1 second do select get_lock("test_lock4", 20);
 ##select sleep(3);
+##--replace_column 1 # 6 #
 ##show processlist;
 ##drop event закачка4;
 ##select release_lock("test_lock4");
 
-#set global event_scheduler=0;
-#select sleep(2);
+##set global event_scheduler=0;
+##select sleep(2);
+##--replace_column 1 # 6 #
 ##show processlist;
-##the following locks for some reason and is a bug, commented for now
 ##select count(*) from mysql.event;
 
 drop database events_test;

sql/event.cc

@@ -704,11 +704,17 @@ evex_load_and_compile_event(THD * thd, sp_name *spn, LEX_STRING definer,
 }
 
 
+/*
+   0 - OK can drop from outside
+   1 - Scheduled from dropping, don't drop from outside
+*/
+
 static int
 evex_remove_from_cache(LEX_STRING *db, LEX_STRING *name, bool use_lock,
                        bool is_drop)
 {
   uint i;
+  int ret= 0;
 
   DBUG_ENTER("evex_remove_from_cache");
   /*
@@ -738,7 +744,8 @@ evex_remove_from_cache(LEX_STRING *db, LEX_STRING *name, bool use_lock,
         DBUG_PRINT("evex_remove_from_cache",
                ("running.defer mem free. is_drop=%d", is_drop));
         et->flags|= EVENT_EXEC_NO_MORE;
-        et->dropped= is_drop;
+        if ((et->dropped= is_drop))
+          ret= 1;
       }
       DBUG_PRINT("evex_remove_from_cache", ("delete from queue"));
       evex_queue_delete_element(&EVEX_EQ_NAME, i);
@@ -751,7 +758,7 @@ evex_remove_from_cache(LEX_STRING *db, LEX_STRING *name, bool use_lock,
   if (use_lock)
     VOID(pthread_mutex_unlock(&LOCK_event_arrays));
 
-  DBUG_RETURN(0);
+  DBUG_RETURN(ret);
 }
 
 
@@ -866,21 +873,25 @@ evex_update_event(THD *thd, event_timed *et, sp_name *new_name,
  Drops an event
 
  SYNOPSIS
-   evex_drop_event()
+   db_drop_event()
      thd             THD
      et              event's name
      drop_if_exists  if set and the event not existing => warning onto the stack
+     rows_affected   affected number of rows is returned heres
           
 */
 
-int
-evex_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
-                uint *rows_affected)
+int db_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
+                  uint *rows_affected)
 {
   TABLE *table;
-  int ret= EVEX_OPEN_TABLE_FAILED;
-  DBUG_ENTER("evex_drop_event");
+  Open_tables_state backup;
+  uint ret;
+
+  DBUG_ENTER("db_drop_event");
+  ret= EVEX_OPEN_TABLE_FAILED;
 
+  thd->reset_n_backup_open_tables_state(&backup);
   if (evex_open_event_table(thd, TL_WRITE, &table))
   {
     my_error(ER_EVENT_OPEN_TABLE_FAILED, MYF(0));
@@ -908,10 +919,6 @@ evex_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
     goto done;
   }
 
-  VOID(pthread_mutex_lock(&LOCK_evex_running));
-  if (evex_is_running)
-    ret= evex_remove_from_cache(&et->dbname, &et->name, true, true);
-  VOID(pthread_mutex_unlock(&LOCK_evex_running));
 
 done:
   /*
@@ -919,6 +926,44 @@ evex_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
     we have to close our thread tables.
   */
   close_thread_tables(thd);
+  thd->restore_backup_open_tables_state(&backup);
+  DBUG_RETURN(ret);
+}
+
+
+/*
+ Drops an event
+
+ SYNOPSIS
+   evex_drop_event()
+     thd             THD
+     et              event's name
+     drop_if_exists  if set and the event not existing => warning onto the stack
+     rows_affected   affected number of rows is returned heres
+          
+*/
+
+int
+evex_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
+                uint *rows_affected)
+{
+  TABLE *table;
+  int ret= 0;
+
+  DBUG_ENTER("evex_drop_event");
+
+
+  VOID(pthread_mutex_lock(&LOCK_evex_running));
+  if (evex_is_running)
+    ret= evex_remove_from_cache(&et->dbname, &et->name, true, true);
+  VOID(pthread_mutex_unlock(&LOCK_evex_running));
+  
+  if (ret == 1)
+    ret= 0;
+  else if (ret == 0)   
+    ret= db_drop_event(thd, et, drop_if_exists, rows_affected);
+  else
+    my_error(ER_UNKNOWN_ERROR, MYF(0));
 
   DBUG_RETURN(ret);
 }

sql/event_priv.h

@@ -40,6 +40,9 @@ evex_db_find_event_aux(THD *thd, const LEX_STRING dbname,
 int 
 event_timed_compare_q(void *vptr, byte* a, byte *b);
 
+int db_drop_event(THD *thd, event_timed *et, bool drop_if_exists,
+                uint *rows_affected);
+
 
 #define EXEC_QUEUE_QUEUE_NAME executing_queue
 #define EXEC_QUEUE_DARR_NAME evex_executing_queue

sql/event_timed.cc

@@ -877,20 +877,10 @@ int
 event_timed::drop(THD *thd)
 {
   TABLE *table;
-  int ret= 0;
+  uint tmp= 0;
   DBUG_ENTER("event_timed::drop");
 
-  if (evex_open_event_table(thd, TL_WRITE, &table))
-    DBUG_RETURN(-1);
-
-  if (evex_db_find_event_aux(thd, dbname, name, definer, table))
-    DBUG_RETURN(-2);
-
-  if ((ret= table->file->ha_delete_row(table->record[0])))
-    DBUG_RETURN(ret);
-    
-  close_thread_tables(thd);
-  DBUG_RETURN(0);
+  DBUG_RETURN(db_drop_event(thd, this, false, &tmp));
 }
 
 

sql/sql_parse.cc

@@ -3723,6 +3723,8 @@ mysql_execute_command(THD *thd)
         res= evex_drop_event(thd, lex->et, lex->drop_if_exists, &rows_affected);
       default:;
       }
+      DBUG_PRINT("info", ("CREATE/ALTER/DROP returned error code=%d af_rows=%d",
+                  res, rows_affected));
       if (!res)
         send_ok(thd, rows_affected);