Bug#28291258 FLUSH STATUS ADDS TWICE TO GLOBAL VALUES

During FLUSH STATUS, the Performance Schema unnecessarily aggregates
session status to global status, causing double counts for NO_FLUSH
status variables.

To avoid this, the class PFS_host no longer aggregates to
global_status_vars for status reset operations such as FLUSH STATUS.

mysql-test/suite/perfschema/r/show_aggregate.result

@@ -510,6 +510,27 @@ variable_name	h1	h2	h3	delta	host	Expected
 Handler_delete	6	0	0	6	6	OK
 Handler_rollback	6	0	0	6	6	OK
 ================================================================================
+TEST 8: FLUSH STATUS should clear account, host and user status
+================================================================================
+
+FLUSH STATUS;
+
+SELECT * FROM status_by_account WHERE user LIKE 'user%' AND variable_name IN ('handler_delete');
+USER	HOST	VARIABLE_NAME	VARIABLE_VALUE
+user1	localhost	Handler_delete	0
+user2	localhost	Handler_delete	0
+user3	localhost	Handler_delete	0
+
+SELECT * FROM status_by_host WHERE host IN ('localhost') AND variable_name IN ('handler_delete');
+HOST	VARIABLE_NAME	VARIABLE_VALUE
+localhost	Handler_delete	0
+
+SELECT * FROM status_by_user WHERE user LIKE 'user%' AND variable_name IN ('handler_delete');
+USER	VARIABLE_NAME	VARIABLE_VALUE
+user1	Handler_delete	0
+user2	Handler_delete	0
+user3	Handler_delete	0
+================================================================================
 CLEANUP
 ================================================================================
 DROP TABLE test.t1;

mysql-test/suite/perfschema/r/show_coverage.result

@@ -102,14 +102,43 @@ SELECT variable_value FROM status_by_thread
 WHERE variable_name = "bytes_received" and thread_id = @thread_id INTO @bytes_after;
 
 # Expect bytes_before > bytes_after
-SELECT @bytes_before > @bytes_after;
-@bytes_before > @bytes_after
+SELECT @bytes_before > @bytes_after AS 'Expect 1';
+Expect 1
 1
 
 # Expect bytes_after is zero
-SELECT @bytes_after;
-@bytes_after
+SELECT @bytes_after AS 'Expect 0';
+Expect 0
 0
 
+# TEST 6
+#
+# Bug#28291258 FLUSH STATUS ADDS TWICE TO GLOBAL VALUES
+#
+
+# Default connection
+
+# First connection
+include/assert.inc [Global value requested from the first session must not change]
+
+# Generate a slow query
+
+SET long_query_time = 2;
+SELECT SLEEP(4);
+SLEEP(4)
+0
+SET long_query_time = @@global.long_query_time;
+
+include/assert.inc [Global value requested from the first session after SLEEP() must increase by 1]
+include/assert.inc [First session value must increase by 1]
+
+# Default connection
+include/assert.inc [Global value requested from the default session after DISCONNECT must remain the same]
+include/assert.inc [Default session value must remain zero]
+
+FLUSH STATUS;
+
+include/assert.inc [Global value requested from the default session after FLUSH must remain the same]
+include/assert.inc [Default session value after FLUSH must remain zero]
 # CLEANUP
 set @@global.show_compatibility_56 = @show_compatibility_56_save;

mysql-test/suite/perfschema/t/show_aggregate.test

@@ -280,6 +280,20 @@ SELECT variable_name, h1, h2, h3, delta, host, IF(host=delta,'OK','ERROR') Expec
 FROM test.status_results
 ORDER BY variable_name;
 
+
+--echo ================================================================================
+--echo TEST 8: FLUSH STATUS should clear account, host and user status
+--echo ================================================================================
+--echo
+FLUSH STATUS;
+--echo
+SELECT * FROM status_by_account WHERE user LIKE 'user%' AND variable_name IN ('handler_delete');
+--echo
+SELECT * FROM status_by_host WHERE host IN ('localhost') AND variable_name IN ('handler_delete');
+--echo
+SELECT * FROM status_by_user WHERE user LIKE 'user%' AND variable_name IN ('handler_delete');
+
+
 --echo ================================================================================
 --echo CLEANUP
 --echo ================================================================================

mysql-test/suite/perfschema/t/show_coverage.test

@@ -7,6 +7,7 @@
 --source include/have_perfschema.inc
 --source include/not_embedded.inc
 --source include/no_protocol.inc
+--source include/count_sessions.inc
 
 select @@global.show_compatibility_56 into @show_compatibility_56_save;
 --echo
@@ -111,14 +112,90 @@ SELECT variable_value FROM status_by_thread
   WHERE variable_name = "bytes_received" and thread_id = @thread_id INTO @bytes_after;
 --echo
 --echo # Expect bytes_before > bytes_after
-SELECT @bytes_before > @bytes_after;
+SELECT @bytes_before > @bytes_after AS 'Expect 1';
 --echo
 --echo # Expect bytes_after is zero
-SELECT @bytes_after;
+SELECT @bytes_after AS 'Expect 0';
 
 disconnect con1;
+--source include/wait_until_count_sessions.inc
+
+
+--echo
+--echo # TEST 6
+--echo #
+--echo # Bug#28291258 FLUSH STATUS ADDS TWICE TO GLOBAL VALUES
+--echo #
+
+--echo
+--echo # Default connection
+--let $initial_global_value = query_get_value(SHOW GLOBAL STATUS LIKE 'Slow_queries', Value, 1)
+
+--source include/count_sessions.inc
 
 --echo
+--echo # First connection
+--connect (con1, localhost, root,,)
+
+## Global value requested from the first session must not change
+--let $current_global_value = query_get_value(SHOW GLOBAL STATUS LIKE 'Slow_queries', Value, 1)
+--let $assert_cond = $current_global_value - $initial_global_value = 0
+--let $assert_text = Global value requested from the first session must not change
+--source include/assert.inc
+
+--echo
+--echo # Generate a slow query
+--echo
+SET long_query_time = 2;
+SELECT SLEEP(4);
+SET long_query_time = @@global.long_query_time;
+--echo
+
+## Global value requested from the first session after SLEEP() must increase by 1
+--let $current_global_value = query_get_value(SHOW GLOBAL STATUS LIKE 'Slow_queries', Value, 1)
+--let $first_session_value = query_get_value(SHOW SESSION STATUS LIKE 'Slow_queries', Value, 1)
+--let $assert_cond = $current_global_value - $initial_global_value = 1
+--let $assert_text = Global value requested from the first session after SLEEP() must increase by 1
+--source include/assert.inc
+--let $assert_cond = $first_session_value = 1
+--let $assert_text = First session value must increase by 1
+--source include/assert.inc
+
+--connection default
+--disconnect con1
+--source include/wait_until_count_sessions.inc
+
+--echo
+--echo # Default connection
+--connection default
+
+## Global value requested from the default session after DISCONNECT must remain the same
+--let $current_global_value = query_get_value(SHOW GLOBAL STATUS LIKE 'Slow_queries', Value, 1)
+--let $default_session_value = query_get_value(SHOW SESSION STATUS LIKE 'Slow_queries', Value, 1)
+--let $assert_cond = $current_global_value - $initial_global_value = 1
+--let $assert_text = Global value requested from the default session after DISCONNECT must remain the same
+--source include/assert.inc
+
+## Default session value must remain zero
+--let $assert_cond = $default_session_value = 0
+--let $assert_text = Default session value must remain zero
+--source include/assert.inc
+
+--echo
+FLUSH STATUS;
+--echo
+
+## Global value requested from the default session after FLUSH must remain the same
+--let $current_global_value = query_get_value(SHOW GLOBAL STATUS LIKE 'Slow_queries', Value, 1)
+--let $default_session_value = query_get_value(SHOW SESSION STATUS LIKE 'Slow_queries', Value, 1)
+--let $assert_cond = $current_global_value - $initial_global_value = 1
+--let $assert_text = Global value requested from the default session after FLUSH must remain the same
+--source include/assert.inc
+
+## Default session value after FLUSH must remain zero
+--let $assert_cond = $default_session_value = 0
+--let $assert_text = Default session value after FLUSH must remain zero
+--source include/assert.inc
+
 --echo # CLEANUP
 set @@global.show_compatibility_56 = @show_compatibility_56_save;
-

storage/perfschema/pfs_host.cc

@@ -1,4 +1,4 @@
-/* Copyright (c) 2010, 2015, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2010, 2018, Oracle and/or its affiliates. All rights reserved.
 
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -274,11 +274,7 @@ void PFS_host::aggregate_memory(bool alive)
 
 void PFS_host::aggregate_status()
 {
-  /*
-    Aggregate STATUS_BY_HOST to:
-    - GLOBAL_STATUS
-  */
-  m_status_stats.aggregate_to(& global_status_var);
+  /* No parent to aggregate to, clean the stats */
   m_status_stats.reset();
 }
 

storage/perfschema/pfs_variable.cc

@@ -1306,8 +1306,6 @@ void reset_pfs_status_stats()
   reset_status_by_account();
   reset_status_by_user();
   reset_status_by_host();
-  /* Clear again, updated by previous aggregations. */
-  reset_global_status();
 }
 
 /** @} */