MWL#90: Subqueries: Inside-out execution for non-semijoin materialized

subqueries that are AND-parts of the WHERE
- First code (needs cleanup).

sql/sql_select.h

@@ -1551,7 +1551,18 @@ public:
   bool union_part; ///< this subselect is part of union 
   bool optimized; ///< flag to avoid double optimization in EXPLAIN
 
+  /* 
+    Subqueries that will need to be converted to semi-join nests (the list 
+    is emptied when conversion is done
+  */
   Array<Item_in_subselect> sj_subselects;
+  
+  /*
+    Subqueries that will need to be converted to JOIN_TABs
+    (Note this is different from the above in the respect that it's part 
+    of WHERE clause or something like that?)
+  */
+  //Array<Item_in_subselect> jtbm_subselects;
 
   /* Temporary tables used to weed-out semi-join duplicates */
   List<TABLE> sj_tmp_tables;
@@ -1575,6 +1586,7 @@ public:
   JOIN(THD *thd_arg, List<Item> &fields_arg, ulonglong select_options_arg,
        select_result *result_arg)
     :fields_list(fields_arg), sj_subselects(thd_arg->mem_root, 4)
+     //jtbm_subselects(thd_arg->mem_root, 4)
   {
     init(thd_arg, fields_arg, select_options_arg, result_arg);
   }