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, 80 insertions, 0 deletions

diff --git a/mysql-test/t/events_stress.test b/mysql-test/t/events_stress.test
new file mode 100644
index 00000000000..f6eed79425c
--- /dev/null
+++ b/mysql-test/t/events_stress.test
@@ -0,0 +1,80 @@
+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;