MWL#182: Explain running statements

- Remove out-of-date comments, add dbug assertions.

sql/filesort.cc

@@ -1242,11 +1242,6 @@ int merge_buffers(SORTPARAM *param, IO_CACHE *from_file,
 
   status_var_increment(thd->status_var.filesort_merge_passes);
   thd->query_plan_fsort_passes++;
-  /*if (param->not_killable)
-  {
-    killed= &not_killable;
-    not_killable= NOT_KILLED;
-  }*/
 
   error=0;
   rec_length= param->rec_length;

sql/my_apc.cc

@@ -86,7 +86,7 @@ void Apc_target::disable()
 
 void Apc_target::enqueue_request(Call_request *qe)
 {
-  //call_queue_size++;
+  mysql_mutex_assert_owner(LOCK_thd_data_ptr);
   if (apc_calls)
   {
     Call_request *after= apc_calls->prev;
@@ -112,12 +112,11 @@ void Apc_target::enqueue_request(Call_request *qe)
 
 void Apc_target::dequeue_request(Call_request *qe)
 {
-  //call_queue_size--;
+  mysql_mutex_assert_owner(LOCK_thd_data_ptr);
   if (apc_calls == qe)
   {
     if ((apc_calls= apc_calls->next) == qe)
     {
-      //DBUG_ASSERT(!call_queue_size);
       apc_calls= NULL;
     }
   }

sql/my_apc.h

@@ -28,7 +28,7 @@ class Apc_target
 {
   mysql_mutex_t *LOCK_thd_data_ptr;
 public:
-  Apc_target() : enabled(0), apc_calls(NULL) /*, call_queue_size(0)*/ {} 
+  Apc_target() : enabled(0), apc_calls(NULL) {} 
   ~Apc_target() { DBUG_ASSERT(!enabled && !apc_calls);}
 
   void init(mysql_mutex_t *target_mutex);

sql/sql_class.cc

@@ -3333,12 +3333,14 @@ void THD::restore_active_arena(Query_arena *set, Query_arena *backup)
 void Show_explain_request::get_explain_data(void *arg)
 {
   Show_explain_request *req= (Show_explain_request*)arg;
-  //TODO: change mem_root to point to request_thd->mem_root.
-  //      Actually, change the ARENA, because we're going to allocate items!
   Query_arena backup_arena;
   THD *target_thd= req->target_thd;
   bool printed_anything= FALSE;
 
+  /* 
+    Change the arena because JOIN::print_explain and co. are going to allocate
+    items. Let them allocate them on our arena.
+  */
   target_thd->set_n_backup_active_arena((Query_arena*)req->request_thd,
                                         &backup_arena);
   

sql/sql_select.cc

@@ -10321,12 +10321,7 @@ void JOIN_TAB::cleanup()
   if (cache)
   {
     cache->free();
-    cache= 0; // psergey: this is why we don't see "Using join cache" in SHOW EXPLAIN
-              //  when it is run for "Using temporary+filesort" queries while they 
-              //  are at reading-from-tmp-table phase.
-              //
-              //  TODO ask igor if this can be just moved to later phase
-              //  (JOIN_CACHE objects themselves are not big, arent they)
+    cache= 0;
   }
   limit= 0;
   if (table)

sql/sql_show.cc

@@ -2092,7 +2092,6 @@ void mysqld_show_explain(THD *thd, ulong thread_id)
       push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
                    ER_YES, explain_req.query_str.c_ptr_safe());
     }
-    //mysql_mutex_unlock(&tmp->LOCK_thd_data);
     if (!bres)
     {
       explain_buf->flush_data();