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MDEV-17251 SHOW STATUS unnecessary calls calc_sum_of_all_status

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1. only call calc_sum_of_all_status() if a global
   SHOW_xxx_STATUS variable is to be returned
2. only lock LOCK_status when copying global_status_var,
   but not when iterating all threads
This commit is contained in:
Sergei Golubchik
2021-01-07 19:37:47 +01:00
parent 4c448836d4
commit 63f9192787
4 changed files with 16 additions and 11 deletions
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20
sql/sql_show.cc
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@ -3580,6 +3580,16 @@ static bool show_status_array(THD *thd, const char *wild,
if (show_type == SHOW_SYS)
mysql_mutex_lock(&LOCK_global_system_variables);
else if (show_type >= SHOW_LONG_STATUS && scope == OPT_GLOBAL &&
!status_var->local_memory_used)
{
mysql_mutex_lock(&LOCK_status);
*status_var= global_status_var;
mysql_mutex_unlock(&LOCK_status);
calc_sum_of_all_status(status_var);
DBUG_ASSERT(status_var->local_memory_used);
}
pos= get_one_variable(thd, var, scope, show_type, status_var,
&charset, buff, &length);
@ -3620,8 +3630,6 @@ uint calc_sum_of_all_status(STATUS_VAR *to)
I_List_iterator<THD> it(threads);
THD *tmp;
/* Get global values as base */
*to= global_status_var;
to->local_memory_used= 0;
/* Add to this status from existing threads */
@ -7586,13 +7594,7 @@ int fill_status(THD *thd, TABLE_LIST *tables, COND *cond)
if (partial_cond)
partial_cond->val_int();
if (scope == OPT_GLOBAL)
{
/* We only hold LOCK_status for summary status vars */
mysql_mutex_lock(&LOCK_status);
calc_sum_of_all_status(&tmp);
mysql_mutex_unlock(&LOCK_status);
}
tmp.local_memory_used= 0; // meaning tmp was not populated yet
mysql_mutex_lock(&LOCK_show_status);
res= show_status_array(thd, wild,