MDEV-4536, MDEV-4042

- Make JOIN::cleanup(true) also work correctly when the query is KILLed
  after join optimization was started but before a query plan was produced

sql/sql_select.cc

@@ -10643,10 +10643,15 @@ void JOIN::cleanup(bool full)
         w/o tables: they don't have some members initialized and
         WALK_OPTIMIZATION_TABS may not work correctly for them.
       */
-      if (table_count) 
+      enum enum_exec_or_opt tabs_kind;
+      if (first_breadth_first_tab(this, WALK_OPTIMIZATION_TABS))
+        tabs_kind= WALK_OPTIMIZATION_TABS;
+      else
+        tabs_kind= WALK_EXECUTION_TABS;
+      if (table_count)
       {
-        for (tab= first_breadth_first_tab(this, WALK_OPTIMIZATION_TABS); tab; 
-             tab= next_breadth_first_tab(this, WALK_OPTIMIZATION_TABS, tab))
+        for (tab= first_breadth_first_tab(this, tabs_kind); tab; 
+             tab= next_breadth_first_tab(this, tabs_kind, tab))
         {
           tab->cleanup();
         }

sql/sql_select.h

@@ -1308,6 +1308,12 @@ public:
     pre_sort_join_tab= NULL;
     emb_sjm_nest= NULL;
     sjm_lookup_tables= 0;
+    /* 
+      The following is needed because JOIN::cleanup(true) may be called for 
+      joins for which JOIN::optimize was aborted with an error before a proper
+      query plan was produced
+    */
+    table_access_tabs= NULL; 
   }
 
   int prepare(Item ***rref_pointer_array, TABLE_LIST *tables, uint wind_num,