Fix for Bug#39854 events_scheduling fails sporadically on pushbuild

Detail:
- Choose the solution that was already in place (before last fix)
  for 6.0
- minor cleanup in comments

mysql-test/r/events_scheduling.result

@@ -62,18 +62,6 @@ CREATE EVENT event_4 ON SCHEDULE EVERY 1 SECOND ENDS NOW() + INTERVAL 1 SECOND
 ON COMPLETION PRESERVE
 DO
 INSERT INTO table_4 VALUES (1);
-SELECT IF(SUM(a) >= 4, 'OK', 'ERROR') FROM table_1;
-IF(SUM(a) >= 4, 'OK', 'ERROR')
-OK
-SELECT IF(SUM(a) >= 4, 'OK', 'ERROR') FROM table_2;
-IF(SUM(a) >= 4, 'OK', 'ERROR')
-OK
-SELECT IF(SUM(a) >= 1, 'OK', 'ERROR') FROM table_3;
-IF(SUM(a) >= 1, 'OK', 'ERROR')
-OK
-SELECT IF(SUM(a) >= 1, 'OK', 'ERROR') FROM table_4;
-IF(SUM(a) >= 1, 'OK', 'ERROR')
-OK
 SELECT IF(TIME_TO_SEC(TIMEDIFF(ENDS,STARTS))=6, 'OK', 'ERROR')
 FROM INFORMATION_SCHEMA.EVENTS
 WHERE EVENT_SCHEMA=DATABASE() AND EVENT_NAME='event_2';

mysql-test/t/events_scheduling.test

@@ -58,8 +58,6 @@ ON COMPLETION PRESERVE
 DO
   INSERT INTO table_4 VALUES (1);
 
-# Wait for the events to fire and check the data afterwards
-
 # Let event_1 insert at least 4 records into the table
 let $wait_condition=select count(*) >= 4 from table_1;
 --source include/wait_condition.inc
@@ -85,25 +83,13 @@ let $wait_condition=select count(*) = 0 from information_schema.events
 where event_name='event_4' and status='enabled';
 --source include/wait_condition.inc
 
-let $wait_condition=SELECT SUM(a) >= 4 FROM table_1;
-source include/wait_condition.inc;
-SELECT IF(SUM(a) >= 4, 'OK', 'ERROR') FROM table_1;
-
-# In case of a testing box under heavy load it cannot be guaranteed that
-# it is really often enough checked if event_2 has to be executed.
-# -> Bug#39854 events_scheduling fails sporadically on pushbuild
-# Therefore we lowered here the original expectation of 5 to 4.
-let $wait_condition=SELECT SUM(a) >= 4 FROM table_2;
-source include/wait_condition.inc;
-SELECT IF(SUM(a) >= 4, 'OK', 'ERROR') FROM table_2;
-
-let $wait_condition=SELECT SUM(a) >= 1 FROM table_3;
-source include/wait_condition.inc;
-SELECT IF(SUM(a) >= 1, 'OK', 'ERROR') FROM table_3;
-
-let $wait_condition=SELECT SUM(a) >= 1 FROM table_4;
-source include/wait_condition.inc;
-SELECT IF(SUM(a) >= 1, 'OK', 'ERROR') FROM table_4;
+#
+# On a busy system the scheduler may skip execution of events,
+# we can't reliably expect that the data in a table to be modified
+# by an event will be exact. Thus we do not SELECT from the tables
+# in this test. See also
+#    Bug#39854 events_scheduling fails sporadically on pushbuild
+#
 
 SELECT IF(TIME_TO_SEC(TIMEDIFF(ENDS,STARTS))=6, 'OK', 'ERROR')
 FROM INFORMATION_SCHEMA.EVENTS