Improve comments around FLUSH STATUS

It's not possible to flush the global status variables in 5.0
Update test case so it works by recording the value of handle_rollback
before and compare it to the value after


mysql-test/r/innodb_mysql.result:
  Update result file
mysql-test/t/innodb_mysql.test:
  It's not possible to reset the global status variables in 5.0 so intead its value
  is recorded and compared to the after value.
  It should not have changed.
sql/mysqld.cc:
  Improve comments
sql/set_var.cc:
  Improve comments
sql/sql_class.cc:
  Improve comments
sql/sql_class.h:
  Improve comments

4 files changed, 19 insertions, 7 deletions

diff --git a/sql/mysqld.cc b/sql/mysqld.cc
index 1dd15398cd1..c84e1f7ee56 100644
--- a/sql/mysqld.cc
+++ b/sql/mysqld.cc
@@ -5997,6 +5997,10 @@ The minimum value for this variable is 4096.",
 };
 
 
+/*
+  Variables shown by SHOW STATUS in alphabetical order
+*/
+
 struct show_var_st status_vars[]= {
   {"Aborted_clients",          (char*) &aborted_threads,        SHOW_LONG},
   {"Aborted_connects",         (char*) &aborted_connects,       SHOW_LONG},
@@ -7466,15 +7470,19 @@ void refresh_status(THD *thd)
 {
   pthread_mutex_lock(&LOCK_status);
 
-  /* We must update the global status before cleaning up the thread */
+  /* Add thread's status variabes to global status */
   add_to_status(&global_status_var, &thd->status_var);
+
+  /* Reset thread's status variables */
   bzero((char*) &thd->status_var, sizeof(thd->status_var));
 
+  /* Reset some global variables */
   for (struct show_var_st *ptr=status_vars; ptr->name; ptr++)
   {
     if (ptr->type == SHOW_LONG)
       *(ulong*) ptr->value= 0;
   }
+
   /* Reset the counters of all key caches (default and named). */
   process_key_caches(reset_key_cache_counters);
   pthread_mutex_unlock(&LOCK_status);
diff --git a/sql/set_var.cc b/sql/set_var.cc
index df0c69260e7..55c62a9a5a5 100644
--- a/sql/set_var.cc
+++ b/sql/set_var.cc
@@ -804,7 +804,7 @@ sys_var *sys_variables[]=
 
 
 /*
-  Variables shown by SHOW variables in alphabetical order
+  Variables shown by SHOW VARIABLES in alphabetical order
 */
 
 struct show_var_st init_vars[]= {
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index f5bab1d17f4..ba2f525a4a4 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -464,14 +464,13 @@ THD::~THD()
 
 void add_to_status(STATUS_VAR *to_var, STATUS_VAR *from_var)
 {
-  ulong *end= (ulong*) ((byte*) to_var + offsetof(STATUS_VAR,
-						  last_system_status_var) +
+  ulong *end= (ulong*) ((byte*) to_var +
+                        offsetof(STATUS_VAR, last_system_status_var) +
 			sizeof(ulong));
   ulong *to= (ulong*) to_var, *from= (ulong*) from_var;
 
   while (to != end)
     *(to++)+= *(from++);
-  /* it doesn't make sense to add last_query_cost values */
 }
 
 
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 62cfb0119aa..c7bdfbd7ea7 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -646,12 +646,17 @@ typedef struct system_status_var
   ulong com_stmt_reset;
   ulong com_stmt_close;
 
+  /*
+    Status variables which it does not make sense to add to
+    global status variable counter
+  */
   double last_query_cost;
 } STATUS_VAR;
 
 /*
-  This is used for 'show status'. It must be updated to the last ulong
-  variable in system_status_var
+  This is used for 'SHOW STATUS'. It must be updated to the last ulong
+  variable in system_status_var which is makes sens to add to the global
+  counter
 */
 
 #define last_system_status_var com_stmt_close