Bug#21788887 HANDLER_EXTERNAL_LOCK, CREATED_TMP_TABLES SHOW ACTUAL VALUE +1

Use status var snapshot from before the start of the SHOW STATUS query to
avoid status counter updates caused by the query itself.

Author: Christopher Powers

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

@@ -32,6 +32,22 @@ select 2;
 SHOW STATUS LIKE 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	0.000000
+================================================================================
+SHOW_COMPATIBILITY_56 = ON
+================================================================================
+flush status;
+set global show_compatibility_56 = on;
+SHOW STATUS LIKE 'Created_tmp_tables';
+Variable_name	Value
+Created_tmp_tables	0
+
+================================================================================
+SHOW_COMPATIBILITY_56 = OFF
+================================================================================
+set global show_compatibility_56 = off;
+SHOW STATUS LIKE 'Created_tmp_tables';
+Variable_name	Value
+Created_tmp_tables	0
 
 ================================================================================
 CLEAN UP

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

@@ -26,6 +26,22 @@ SHOW STATUS LIKE 'Last_query_partial_plans';
 select 2;
 SHOW STATUS LIKE 'Last_query_cost';
 
+
+--echo ================================================================================
+--echo SHOW_COMPATIBILITY_56 = ON
+--echo ================================================================================
+flush status;
+set global show_compatibility_56 = on;
+SHOW STATUS LIKE 'Created_tmp_tables';
+
+--echo
+--echo ================================================================================
+--echo SHOW_COMPATIBILITY_56 = OFF
+--echo ================================================================================
+set global show_compatibility_56 = off;
+
+SHOW STATUS LIKE 'Created_tmp_tables';
+
 --echo
 --echo ================================================================================
 --echo CLEAN UP

storage/perfschema/pfs_variable.cc

@@ -889,6 +889,20 @@ bool PFS_status_variable_cache::do_initialize_session(void)
   return ret;
 }
 
+/**
+  For the current THD, use initial_status_vars taken from before the query start.
+*/
+STATUS_VAR *PFS_status_variable_cache::set_status_vars(void)
+{
+  STATUS_VAR *status_vars;
+  if (m_safe_thd == m_current_thd && m_current_thd->initial_status_var != NULL)
+    status_vars= m_current_thd->initial_status_var;
+  else
+    status_vars= &m_safe_thd->status_var;
+
+  return status_vars;
+}
+
 /**
   Build cache for GLOBAL status variables using values totaled from all threads.
 */
@@ -967,8 +981,9 @@ int PFS_status_variable_cache::do_materialize_all(THD* unsafe_thd)
     /*
       Build the status variable cache using the SHOW_VAR array as a reference.
       Use the status values from the THD protected by the thread manager lock.
-     */
-    manifest(m_safe_thd, m_show_var_array.begin(), &m_safe_thd->status_var, "", false, false);
+    */
+    STATUS_VAR *status_vars= set_status_vars();
+    manifest(m_safe_thd, m_show_var_array.begin(), status_vars, "", false, false);
 
     /* Release lock taken in get_THD(). */
     mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
@@ -1012,8 +1027,9 @@ int PFS_status_variable_cache::do_materialize_session(THD* unsafe_thd)
     /*
       Build the status variable cache using the SHOW_VAR array as a reference.
       Use the status values from the THD protected by the thread manager lock.
-     */
-    manifest(m_safe_thd, m_show_var_array.begin(), &m_safe_thd->status_var, "", false, true);
+    */
+    STATUS_VAR *status_vars= set_status_vars();
+    manifest(m_safe_thd, m_show_var_array.begin(), status_vars, "", false, true);
 
     /* Release lock taken in get_THD(). */
     mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);
@@ -1054,7 +1070,8 @@ int PFS_status_variable_cache::do_materialize_session(PFS_thread *pfs_thread)
       Build the status variable cache using the SHOW_VAR array as a reference.
       Use the status values from the THD protected by the thread manager lock.
     */
-    manifest(m_safe_thd, m_show_var_array.begin(), &m_safe_thd->status_var, "", false, true);
+    STATUS_VAR *status_vars= set_status_vars();
+    manifest(m_safe_thd, m_show_var_array.begin(), status_vars, "", false, true);
 
     /* Release lock taken in get_THD(). */
     mysql_mutex_unlock(&m_safe_thd->LOCK_thd_data);

storage/perfschema/pfs_variable.h

@@ -678,6 +678,9 @@ class PFS_status_variable_cache : public PFS_variable_cache<Status_variable>
   /* Build status variable name with prefix. Return copy of the string. */
   char *make_show_var_name(const char* prefix, const char* name);
 
+  /* For the current THD, use initial_status_vars taken from before the query start. */
+  STATUS_VAR *set_status_vars(void);
+
   /* Build the list of status variables from SHOW_VAR array. */
   void manifest(THD *thd, const SHOW_VAR *show_var_array,
                 STATUS_VAR *status_var_array, const char *prefix, bool nested_array, bool strict);