Fix for Bug#35074: max_used_connections is not correct.

The problem was that number of threads was used to calculate
max_used_connections.

The fix is to use number of active connections.

mysql-test/r/connect.result

@@ -162,14 +162,48 @@ root
 
 # -- Resetting variables...
 SET GLOBAL max_connections = 151;
+
+# -- Stopping Event Scheduler...
 SET GLOBAL event_scheduler = OFF;
+# -- Waiting for Event Scheduler to stop...
 
 # -- That's it. Closing connections...
 
 # -- Restoring default connection...
 
+# -- Waiting for connections to close...
+
+DROP USER mysqltest_u1@localhost;
+
 # -- End of Bug#33507.
 
+# -- Bug#35074: max_used_connections is not correct. 
+
+FLUSH STATUS;
+
+SHOW STATUS LIKE 'max_used_connections';
+Variable_name	Value
+Max_used_connections	1
+
+# -- Starting Event Scheduler...
+SET GLOBAL event_scheduler = ON;
+# -- Waiting for Event Scheduler to start...
+
+# -- Opening a new connection to check max_used_connections...
+
+# -- Check that max_used_connections hasn't changed.
+SHOW STATUS LIKE 'max_used_connections';
+Variable_name	Value
+Max_used_connections	2
+
+# -- Closing new connection...
+
+# -- Stopping Event Scheduler...
+SET GLOBAL event_scheduler = OFF;
+# -- Waiting for Event Scheduler to stop...
+
+# -- End of Bug#35074.
+
 # ------------------------------------------------------------------
 # -- End of 5.1 tests
 # ------------------------------------------------------------------

mysql-test/t/connect.test

@@ -209,22 +209,97 @@ SELECT user FROM information_schema.processlist ORDER BY id;
 --echo # -- Resetting variables...
 
 --eval SET GLOBAL max_connections = $saved_max_connections
+
+--echo
+--echo # -- Stopping Event Scheduler...
 SET GLOBAL event_scheduler = OFF;
 
+--echo # -- Waiting for Event Scheduler to stop...
+let $wait_condition =
+  SELECT COUNT(*) = 0
+  FROM information_schema.processlist
+  WHERE user = 'event_scheduler';
+--source include/wait_condition.inc
+
 --echo
 --echo # -- That's it. Closing connections...
 --disconnect con_1
 --disconnect con_2
+--disconnect con_3
 --disconnect con_super_1
 
 --echo
 --echo # -- Restoring default connection...
 --connect (default,localhost,root,,test)
 
+--echo
+--echo # -- Waiting for connections to close...
+let $wait_condition =
+  SELECT COUNT(*) = 1
+  FROM information_schema.processlist
+  WHERE db = 'test';
+--source include/wait_condition.inc
+
+--echo
+DROP USER mysqltest_u1@localhost;
+
 --echo
 --echo # -- End of Bug#33507.
 --echo
 
+###########################################################################
+
+--echo # -- Bug#35074: max_used_connections is not correct. 
+--echo
+
+FLUSH STATUS;
+
+--echo
+SHOW STATUS LIKE 'max_used_connections';
+
+--echo
+--echo # -- Starting Event Scheduler...
+SET GLOBAL event_scheduler = ON;
+
+--echo # -- Waiting for Event Scheduler to start...
+let $wait_condition =
+  SELECT COUNT(*) = 1
+  FROM information_schema.processlist
+  WHERE user = 'event_scheduler';
+--source include/wait_condition.inc
+
+# NOTE: We should use a new connection here instead of reconnect in order to
+# avoid races (we can not for sure when the connection being disconnected is
+# actually disconnected on the server).
+
+--echo
+--echo # -- Opening a new connection to check max_used_connections...
+--connect (con_1,localhost,root)
+
+--echo
+--echo # -- Check that max_used_connections hasn't changed.
+SHOW STATUS LIKE 'max_used_connections';
+
+--echo
+--echo # -- Closing new connection...
+--disconnect con_1
+--connection default
+
+--echo
+--echo # -- Stopping Event Scheduler...
+SET GLOBAL event_scheduler = OFF;
+
+--echo # -- Waiting for Event Scheduler to stop...
+let $wait_condition =
+  SELECT COUNT(*) = 0
+  FROM information_schema.processlist
+  WHERE user = 'event_scheduler';
+--source include/wait_condition.inc
+
+--echo
+--echo # -- End of Bug#35074.
+--echo
+
 --echo # ------------------------------------------------------------------
 --echo # -- End of 5.1 tests
 --echo # ------------------------------------------------------------------

sql/mysqld.cc

@@ -4776,6 +4776,9 @@ static void create_new_thread(THD *thd)
 
   ++connection_count;
 
+  if (connection_count > max_used_connections)
+    max_used_connections= connection_count;
+
   pthread_mutex_unlock(&LOCK_connection_count);
 
   /* Start a new thread to handle connection. */
@@ -4791,9 +4794,6 @@ static void create_new_thread(THD *thd)
 
   thread_count++;
 
-  if (thread_count - delayed_insert_threads > max_used_connections)
-    max_used_connections= thread_count - delayed_insert_threads;
-
   thread_scheduler.add_connection(thd);
 
   DBUG_VOID_RETURN;