fixed subquery with PS (BUG#2462)

fixed UNION preparation


sql/item.cc:
  debug output added
sql/item.h:
  debug output added
sql/item_cmpfunc.cc:
  correct cleunup() for Item_in_optimizer
sql/item_cmpfunc.h:
  correct cleunup() for Item_in_optimizer
  debug output added
sql/item_func.h:
  debug output added
sql/item_subselect.cc:
  support of prepared statemnts added - mostly memorry allocation manegement, only one trabsformatio & correct cleupup()
sql/item_subselect.h:
  support of prepared statemnts added - mostly memorry allocation manegement, only one trabsformatio & correct cleupup()
sql/item_sum.cc:
  debug output added
sql/item_sum.h:
  debug output added
sql/sql_class.cc:
  function to switch allocation arena for Items
sql/sql_class.h:
  function to switch allocation arena for Items
  pointer on current prepared statement added
sql/sql_lex.cc:
  comment fixed
sql/sql_lex.h:
  item cleanup support
sql/sql_prepare.cc:
  - fixed preparation of PS to avoid storing junk in its memory + correct work with union
  - fixed tables cleanup for UNION & subqueries
sql/sql_select.cc:
  removed condition which is always true for now
  fixed layout
sql/sql_union.cc:
  support of UNION subquery cleanup
tests/client_test.c:
  test of repeatable subqueries
  test of correct UNION initialisation

17 files changed, 359 insertions, 120 deletions

diff --git a/sql/item.cc b/sql/item.cc
index 09328dfbf07..44878329373 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -966,8 +966,10 @@ bool Item_field::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
 
 void Item_field::cleanup()
 {
+  DBUG_ENTER("Item_field::cleanup");
   Item_ident::cleanup();
   field= result_field= 0;
+  DBUG_VOID_RETURN;
 }
 
 void Item::init_make_field(Send_field *tmp_field,
@@ -1610,9 +1612,11 @@ bool Item_ref::fix_fields(THD *thd,TABLE_LIST *tables, Item **reference)
 
 void Item_ref::cleanup()
 {
+  DBUG_ENTER("Item_ref::cleanup");
   Item_ident::cleanup();
   if (hook_ptr)
     *hook_ptr= orig_item;
+  DBUG_VOID_RETURN;
 }
 
 
diff --git a/sql/item.h b/sql/item.h
index a5648c5889b..a1c7f2e16f1 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -128,7 +128,13 @@ public:
   virtual ~Item() { name=0; }		/*lint -e1509 */
   void set_name(const char *str,uint length, CHARSET_INFO *cs);
   void init_make_field(Send_field *tmp_field,enum enum_field_types type);
-  virtual void cleanup() { fixed=0; }
+  virtual void cleanup()
+  {
+    DBUG_ENTER("Item::cleanup");
+    DBUG_PRINT("info", ("Type: %d", (int)type()));
+    fixed=0;
+    DBUG_VOID_RETURN;
+  }
   virtual void make_field(Send_field *field);
   virtual bool fix_fields(THD *, struct st_table_list *, Item **);
   virtual int save_in_field(Field *field, bool no_conversions);
@@ -996,8 +1002,10 @@ public:
   void bring_value();
   void cleanup()
   {
+    DBUG_ENTER("Item_cache_row::cleanup");
     Item_cache::cleanup();
     values= 0;
+    DBUG_VOID_RETURN;
   }
 };
 
@@ -1023,8 +1031,10 @@ public:
   Field *example() { return field_example; }
   void cleanup()
   {
+    DBUG_ENTER("Item_type_holder::cleanup");
     Item::cleanup();
     item_type= orig_type;
+    DBUG_VOID_RETURN;
   }
 };
 
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 0b9c7f8d92a..ae91e1fb437 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -484,6 +484,14 @@ longlong Item_in_optimizer::val_int()
   return tmp;
 }
 
+void Item_in_optimizer::cleanup()
+{
+  DBUG_ENTER("Item_in_optimizer::cleanup");
+  Item_bool_func::cleanup();
+  cache= 0;
+  DBUG_VOID_RETURN;
+}
+
 bool Item_in_optimizer::is_null()
 {
   cache->store(args[0]);
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 7079fcf193d..5235a94c00a 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -105,6 +105,7 @@ public:
     Item_in_optimizer return NULL, else it evaluate Item_in_subselect.
   */
   longlong val_int();
+  void cleanup();
   const char *func_name() const { return "<in_optimizer>"; }
   Item_cache **get_cache() { return &cache; }
 };
@@ -207,9 +208,11 @@ public:
   }
   void cleanup()
   {
+    DBUG_ENTER("Item_bool_rowready_func2::cleanup");
     Item_bool_func2::cleanup();
     tmp_arg[0]= orig_a;
     tmp_arg[1]= orig_b;
+    DBUG_VOID_RETURN;
   }
 };
 
@@ -718,10 +721,12 @@ class Item_func_in :public Item_int_func
   void fix_length_and_dec();
   void cleanup()
   {
+    DBUG_ENTER("Item_func_in::cleanup");
     delete array;
     delete in_item;
     array= 0;
     in_item= 0;
+    DBUG_VOID_RETURN;
   }
   optimize_type select_optimize() const
     { return array ? OPTIMIZE_KEY : OPTIMIZE_NONE; }
diff --git a/sql/item_func.h b/sql/item_func.h
index be20a9b4fc7..71492164a3e 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -991,6 +991,7 @@ public:
        join_key(0), ft_handler(0), table(0), master(0), concat(0) { }
   void cleanup()
   {
+    DBUG_ENTER("Item_func_match");
     if (!master && ft_handler)
     {
       ft_handler->please->close_search(ft_handler);
@@ -1001,6 +1002,7 @@ public:
     }
     if (concat)
       delete concat;
+    DBUG_VOID_RETURN;
   }
   enum Functype functype() const { return FT_FUNC; }
   const char *func_name() const { return "match"; }
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 5b3cc326679..5371030fafa 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -35,9 +35,9 @@ inline Item * and_items(Item* cond, Item *item)
 }
 
 Item_subselect::Item_subselect():
-  Item_result_field(), value_assigned(0), substitution(0),
-  engine(0), used_tables_cache(0), have_to_be_excluded(0),
-  const_item_cache(1), engine_changed(0)
+  Item_result_field(), value_assigned(0), thd(0), substitution(0),
+  engine(0), old_engine(0), used_tables_cache(0), have_to_be_excluded(0),
+  const_item_cache(1), engine_changed(0), changed(0)
 {
   reset();
   /*
@@ -54,9 +54,10 @@ void Item_subselect::init(st_select_lex *select_lex,
 
   DBUG_ENTER("Item_subselect::init");
   DBUG_PRINT("subs", ("select_lex 0x%xl", (ulong) select_lex));
+  unit= select_lex->master_unit();
 
   if (select_lex->next_select())
-    engine= new subselect_union_engine(select_lex->master_unit(), result,
+    engine= new subselect_union_engine(unit, result,
 				       this);
   else
     engine= new subselect_single_select_engine(select_lex, result, this);
@@ -65,8 +66,26 @@ void Item_subselect::init(st_select_lex *select_lex,
 
 void Item_subselect::cleanup()
 {
+  DBUG_ENTER("Item_subselect::cleanup");
   Item_result_field::cleanup();
-  engine->cleanup(); 
+  if (old_engine)
+  {
+    engine->cleanup();
+    engine= old_engine;
+    old_engine= 0;
+  }
+  engine->cleanup();
+  reset();
+  value_assigned= 0;
+  DBUG_VOID_RETURN;
+}
+
+void Item_singlerow_subselect::cleanup()
+{
+  DBUG_ENTER("Item_singlerow_subselect::cleanup");
+  value= 0; row= 0;
+  Item_subselect::cleanup();
+  DBUG_VOID_RETURN;
 }
 
 Item_subselect::~Item_subselect()
@@ -85,13 +104,22 @@ Item_subselect::select_transformer(JOIN *join)
 bool Item_subselect::fix_fields(THD *thd_param, TABLE_LIST *tables, Item **ref)
 {
   engine->set_thd((thd= thd_param));
+  stmt= thd->current_statement;
 
   char const *save_where= thd->where;
   int res= engine->prepare();
+
+  // all transformetion is done (used by prepared statements)
+  changed= 1;
+
   if (!res)
   {
     if (substitution)
     {
+      // did we changed top item of WHERE condition
+      if (unit->outer_select()->where == (*ref))
+	unit->outer_select()->where= substitution; // correct WHERE for PS
+
       (*ref)= substitution;
       substitution->name= name;
       if (have_to_be_excluded)
@@ -240,8 +268,12 @@ void Item_singlerow_subselect::reset()
 Item_subselect::trans_res
 Item_singlerow_subselect::select_transformer(JOIN *join)
 {
+  if (changed)
+    return RES_OK;
+    
   SELECT_LEX *select_lex= join->select_lex;
-  
+  Statement backup;
+
   if (!select_lex->master_unit()->first_select()->next_select() &&
       !select_lex->table_list.elements &&
       select_lex->item_list.elements == 1 &&
@@ -275,20 +307,30 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
     if (join->conds || join->having)
     {
       Item *cond;
+      if (stmt)
+	thd->set_n_backup_item_arena(stmt, &backup);
+
       if (!join->having)
 	cond= join->conds;
       else if (!join->conds)
 	cond= join->having;
       else
 	if (!(cond= new Item_cond_and(join->conds, join->having)))
-	  return RES_ERROR;
+	  goto err;
       if (!(substitution= new Item_func_if(cond, substitution,
 					   new Item_null())))
-	return RES_ERROR;
+	goto err;
     }
+    if (stmt)
+      thd->restore_backup_item_arena(&backup);
     return RES_REDUCE;
   }
   return RES_OK;
+  
+err:
+  if (stmt)
+    thd->restore_backup_item_arena(&backup);
+  return RES_ERROR;
 }
 
 void Item_singlerow_subselect::store(uint i, Item *item)
@@ -550,15 +592,22 @@ Item_in_subselect::single_value_transformer(JOIN *join,
 {
   DBUG_ENTER("Item_in_subselect::single_value_transformer");
 
+  if (changed)
+  {
+    DBUG_RETURN(RES_OK);
+  }
+
   SELECT_LEX *select_lex= join->select_lex;
+  Statement backup;
 
-  THD *thd_tmp= join->thd;
-  thd_tmp->where= "scalar IN/ALL/ANY subquery";
+  thd->where= "scalar IN/ALL/ANY subquery";
+  if (stmt)
+    thd->set_n_backup_item_arena(stmt, &backup);
 
   if (select_lex->item_list.elements > 1)
   {
     my_error(ER_OPERAND_COLUMNS, MYF(0), 1);
-    DBUG_RETURN(RES_ERROR);
+    goto err;
   }
 
   if ((abort_on_null || (upper_not && upper_not->top_level())) &&
@@ -567,7 +616,7 @@ Item_in_subselect::single_value_transformer(JOIN *join,
     if (substitution)
     {
       // It is second (third, ...) SELECT of UNION => All is done
-      DBUG_RETURN(RES_OK);
+      goto ok;
     }
 
     Item *subs;
@@ -597,10 +646,9 @@ Item_in_subselect::single_value_transformer(JOIN *join,
       select_lex->item_list.empty();
       select_lex->item_list.push_back(item);
     
-      if (item->fix_fields(thd_tmp, join->tables_list, &item))
-      {
-	DBUG_RETURN(RES_ERROR);
-      }
+      if (item->fix_fields(thd, join->tables_list, &item))
+	goto err;
+
       subs= new Item_singlerow_subselect(select_lex);
     }
     else
@@ -611,16 +659,16 @@ Item_in_subselect::single_value_transformer(JOIN *join,
       subs= new Item_maxmin_subselect(this, select_lex, func->l_op());
     }
     // left expression belong to outer select
-    SELECT_LEX *current= thd_tmp->lex->current_select, *up;
-    thd_tmp->lex->current_select= up= current->return_after_parsing();
-    if (left_expr->fix_fields(thd_tmp, up->get_table_list(), &left_expr))
+    SELECT_LEX *current= thd->lex->current_select, *up;
+    thd->lex->current_select= up= current->return_after_parsing();
+    if (left_expr->fix_fields(thd, up->get_table_list(), &left_expr))
     {
-      thd_tmp->lex->current_select= current;
-      DBUG_RETURN(RES_ERROR);
+      thd->lex->current_select= current;
+      goto err;
     }
-    thd_tmp->lex->current_select= current;
+    thd->lex->current_select= current;
     substitution= func->create(left_expr, subs);
-    DBUG_RETURN(RES_OK);
+    goto ok;
   }
 
   if (!substitution)
@@ -629,16 +677,16 @@ Item_in_subselect::single_value_transformer(JOIN *join,
     SELECT_LEX_UNIT *unit= select_lex->master_unit();
     substitution= optimizer= new Item_in_optimizer(left_expr, this);
 
-    SELECT_LEX *current= thd_tmp->lex->current_select, *up;
+    SELECT_LEX *current= thd->lex->current_select, *up;
 
-    thd_tmp->lex->current_select= up= current->return_after_parsing();
+    thd->lex->current_select= up= current->return_after_parsing();
     //optimizer never use Item **ref => we can pass 0 as parameter
-    if (!optimizer || optimizer->fix_left(thd_tmp, up->get_table_list(), 0))
+    if (!optimizer || optimizer->fix_left(thd, up->get_table_list(), 0))
     {
-      thd_tmp->lex->current_select= current;
-      DBUG_RETURN(RES_ERROR);
+      thd->lex->current_select= current;
+      goto err;
     }
-    thd_tmp->lex->current_select= current;
+    thd->lex->current_select= current;
 
     /*
       As far as  Item_ref_in_optimizer do not substitude itself on fix_fields
@@ -665,12 +713,12 @@ Item_in_subselect::single_value_transformer(JOIN *join,
 						select_lex->ref_pointer_array,
 						(char *)"<ref>",
 						this->full_name()));
-    join->having= and_items(join->having, item);
+    select_lex->having= join->having= and_items(join->having, item);
     select_lex->having_fix_field= 1;
-    if (join->having->fix_fields(thd_tmp, join->tables_list, &join->having))
+    if (join->having->fix_fields(thd, join->tables_list, &join->having))
     {
       select_lex->having_fix_field= 0;
-      DBUG_RETURN(RES_ERROR);
+      goto err;
     }
     select_lex->having_fix_field= 0;
   }
@@ -687,39 +735,42 @@ Item_in_subselect::single_value_transformer(JOIN *join,
       if (!abort_on_null)
       {
 	having= new Item_is_not_null_test(this, having);
-	join->having= (join->having ?
-		       new Item_cond_and(having, join->having) :
-		       having);
+	select_lex->having=
+	  join->having= (join->having ?
+			 new Item_cond_and(having, join->having) :
+			 having);
 	select_lex->having_fix_field= 1;
-	if (join->having->fix_fields(thd_tmp, join->tables_list,
+	if (join->having->fix_fields(thd, join->tables_list,
 				     &join->having))
 	{
 	  select_lex->having_fix_field= 0;
-	  DBUG_RETURN(RES_ERROR);
+	  goto err;
 	}
 	select_lex->having_fix_field= 0;
 	item= new Item_cond_or(item,
 			       new Item_func_isnull(isnull));
       }
       item->name= (char *)in_additional_cond;
-      join->conds= and_items(join->conds, item);
-      if (join->conds->fix_fields(thd_tmp, join->tables_list, &join->conds))
-	DBUG_RETURN(RES_ERROR);
+      select_lex->where= join->conds= and_items(join->conds, item);
+      if (join->conds->fix_fields(thd, join->tables_list, &join->conds))
+	goto err;
     }
     else
     {
       if (select_lex->master_unit()->first_select()->next_select())
       {
-	join->having= func->create(expr, 
-				   new Item_null_helper(this, item,
-							(char *)"<no matter>",
-							(char *)"<result>"));
+	select_lex->having=
+	  join->having=
+	  func->create(expr, 
+		       new Item_null_helper(this, item,
+					    (char *)"<no matter>",
+					    (char *)"<result>"));
 	select_lex->having_fix_field= 1;
-	if (join->having->fix_fields(thd_tmp, join->tables_list,
+	if (join->having->fix_fields(thd, join->tables_list,
 				     &join->having))
 	{
 	  select_lex->having_fix_field= 0;
-	  DBUG_RETURN(RES_ERROR);
+	  goto err;
 	}
 	select_lex->having_fix_field= 0;
       }
@@ -730,18 +781,29 @@ Item_in_subselect::single_value_transformer(JOIN *join,
 	// fix_field of item will be done in time of substituting 
 	substitution= item;
 	have_to_be_excluded= 1;
-	if (thd_tmp->lex->describe)
+	if (thd->lex->describe)
 	{
 	  char warn_buff[MYSQL_ERRMSG_SIZE];
 	  sprintf(warn_buff, ER(ER_SELECT_REDUCED), select_lex->select_number);
-	  push_warning(thd_tmp, MYSQL_ERROR::WARN_LEVEL_NOTE,
+	  push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
 		       ER_SELECT_REDUCED, warn_buff);
 	}
+	if (stmt)
+	  thd->set_item_arena(&backup);
 	DBUG_RETURN(RES_REDUCE);
       }
     }
   }
+
+ok:
+  if (stmt)
+    thd->restore_backup_item_arena(&backup);
   DBUG_RETURN(RES_OK);
+
+err:
+  if (stmt)
+    thd->restore_backup_item_arena(&backup);
+  DBUG_RETURN(RES_ERROR);
 }
 
 
@@ -750,15 +812,23 @@ Item_in_subselect::row_value_transformer(JOIN *join)
 {
   DBUG_ENTER("Item_in_subselect::row_value_transformer");
 
-  THD *thd_tmp= join->thd;
-  thd_tmp->where= "row IN/ALL/ANY subquery";
+  if (changed)
+  {
+    DBUG_RETURN(RES_OK);
+  }
+  Statement backup;
+  Item *item= 0;
+
+  thd->where= "row IN/ALL/ANY subquery";
+  if (stmt)
+    thd->set_n_backup_item_arena(stmt, &backup);  
 
   SELECT_LEX *select_lex= join->select_lex;
 
   if (select_lex->item_list.elements != left_expr->cols())
   {
     my_error(ER_OPERAND_COLUMNS, MYF(0), left_expr->cols());
-    DBUG_RETURN(RES_ERROR);
+    goto err;
   }
 
   if (!substitution)
@@ -767,62 +837,68 @@ Item_in_subselect::row_value_transformer(JOIN *join)
     SELECT_LEX_UNIT *unit= select_lex->master_unit();
     substitution= optimizer= new Item_in_optimizer(left_expr, this);
 
-    SELECT_LEX *current= thd_tmp->lex->current_select, *up;
-    thd_tmp->lex->current_select= up= current->return_after_parsing();
+    SELECT_LEX *current= thd->lex->current_select, *up;
+    thd->lex->current_select= up= current->return_after_parsing();
     //optimizer never use Item **ref => we can pass 0 as parameter
-    if (!optimizer || optimizer->fix_left(thd_tmp, up->get_table_list(), 0))
+    if (!optimizer || optimizer->fix_left(thd, up->get_table_list(), 0))
     {
-      thd_tmp->lex->current_select= current;
-      DBUG_RETURN(RES_ERROR);
+      thd->lex->current_select= current;
+      goto err;
     }
-    thd_tmp->lex->current_select= current;
+    thd->lex->current_select= current;
     unit->uncacheable|= UNCACHEABLE_DEPENDENT;
   }
 
-  uint n= left_expr->cols();
-
   select_lex->uncacheable|= UNCACHEABLE_DEPENDENT;
-  select_lex->setup_ref_array(thd_tmp,
+  select_lex->setup_ref_array(thd,
 			      select_lex->order_list.elements +
 			      select_lex->group_list.elements);
-  Item *item= 0;
-  List_iterator_fast<Item> li(select_lex->item_list);
-  for (uint i= 0; i < n; i++)
   {
-    Item *func= new Item_ref_null_helper(this, 
-					 select_lex->ref_pointer_array+i,
-					 (char *) "<no matter>",
-					 (char *) "<list ref>");
-    func=
-      eq_creator.create(new Item_ref((*optimizer->get_cache())->
-				     addr(i),
-				     NULL,
-				     (char *)"<no matter>",
+    uint n= left_expr->cols();
+    List_iterator_fast<Item> li(select_lex->item_list);
+    for (uint i= 0; i < n; i++)
+    {
+      Item *func= new Item_ref_null_helper(this, 
+					   select_lex->ref_pointer_array+i,
+					   (char *) "<no matter>",
+					   (char *) "<list ref>");
+      func=
+	eq_creator.create(new Item_ref((*optimizer->get_cache())->
+				       addr(i),
+				       NULL,
+				       (char *)"<no matter>",
 				     (char *)in_left_expr_name),
-			func);
-    item= and_items(item, func);
+			  func);
+      item= and_items(item, func);
+    }
   }
-
   if (join->having || select_lex->with_sum_func ||
       select_lex->group_list.first ||
       !select_lex->table_list.elements)
   {
-    join->having= and_items(join->having, item);
+    select_lex->having= join->having= and_items(join->having, item);
     select_lex->having_fix_field= 1;
-    if (join->having->fix_fields(thd_tmp, join->tables_list, &join->having))
+    if (join->having->fix_fields(thd, join->tables_list, &join->having))
     {
       select_lex->having_fix_field= 0;
-      DBUG_RETURN(RES_ERROR);
+      goto err;
     }
     select_lex->having_fix_field= 0;
   }
   else
   {
-    join->conds= and_items(join->conds, item);
-    if (join->conds->fix_fields(thd_tmp, join->tables_list, &join->having))
-      DBUG_RETURN(RES_ERROR);
+    select_lex->where= join->conds= and_items(join->conds, item);
+    if (join->conds->fix_fields(thd, join->tables_list, &join->having))
+      goto err;
   }
+  if (stmt)
+    thd->restore_backup_item_arena(&backup);
   DBUG_RETURN(RES_OK);
+
+err:
+  if (stmt)
+    thd->restore_backup_item_arena(&backup);
+  DBUG_RETURN(RES_ERROR);
 }
 
 
@@ -894,13 +970,30 @@ subselect_single_select_engine(st_select_lex *select,
   this->select_lex= select_lex;
 }
 
+
 void subselect_single_select_engine::cleanup()
 {
-  prepared= 0;
-  optimized= 0;
-  executed= 0;
+  DBUG_ENTER("subselect_single_select_engine::cleanup");
+  prepared= optimized= executed= 0;
+  DBUG_VOID_RETURN;
+}
+
+
+void subselect_union_engine::cleanup()
+{
+  DBUG_ENTER("subselect_union_engine::cleanup");
+  unit->reinit_exec_mechanism();
+  DBUG_VOID_RETURN;
 }
 
+
+void subselect_uniquesubquery_engine::cleanup()
+{
+  DBUG_ENTER("subselect_uniquesubquery_engine::cleanup");
+  DBUG_VOID_RETURN;
+}
+
+
 subselect_union_engine::subselect_union_engine(st_select_lex_unit *u,
 					       select_subselect *result_arg,
 					       Item_subselect *item_arg)
diff --git a/sql/item_subselect.h b/sql/item_subselect.h
index dc3d07540da..d550cde64b7 100644
--- a/sql/item_subselect.h
+++ b/sql/item_subselect.h
@@ -26,6 +26,7 @@ class JOIN;
 class select_subselect;
 class subselect_engine;
 class Item_bool_func2;
+class Statement;
 
 /* base class for subselects */
 
@@ -35,22 +36,30 @@ class Item_subselect :public Item_result_field
 protected:
   /* thread handler, will be assigned in fix_fields only */
   THD *thd;
+  /* prepared statement, or 0 */
+  Statement *stmt;
   /* substitution instead of subselect in case of optimization */
   Item *substitution;
+  /* unit of subquery */
+  st_select_lex_unit *unit;
   /* engine that perform execution of subselect (single select or union) */
   subselect_engine *engine;
+  /* old engine if engine was changed */
+  subselect_engine *old_engine;
   /* cache of used external tables */
   table_map used_tables_cache; 
   /* allowed number of columns (1 for single value subqueries) */
   uint max_columns;
   /* work with 'substitution' */
   bool have_to_be_excluded;
-  /* cache of constante state */
+  /* cache of constant state */
   bool const_item_cache;
 
 public:
   /* changed engine indicator */
   bool engine_changed;
+  /* subquery is transformed */
+  bool changed;
 
   enum trans_res {RES_OK, RES_REDUCE, RES_ERROR};
   enum subs_type {UNKNOWN_SUBS, SINGLEROW_SUBS,
@@ -94,6 +103,7 @@ public:
   void print(String *str);
   bool change_engine(subselect_engine *eng)
   {
+    old_engine= engine;
     engine= eng;
     engine_changed= 1;
     return eng == 0;
@@ -116,6 +126,7 @@ public:
   Item_singlerow_subselect(st_select_lex *select_lex);
   Item_singlerow_subselect() :Item_subselect(), value(0), row (0) {}
 
+  void cleanup();
   subs_type substype() { return SINGLEROW_SUBS; }
 
   void reset();
@@ -200,13 +211,6 @@ public:
      
   {}
 
-  void cleanup()
-  {
-    Item_exists_subselect::cleanup();
-    abort_on_null= 0;
-    transformed= 0;
-    upper_not= 0;
-  }
   subs_type substype() { return IN_SUBS; }
   void reset() 
   {
@@ -269,7 +273,7 @@ public:
     maybe_null= 0;
   }
   virtual ~subselect_engine() {}; // to satisfy compiler
-  virtual void cleanup() {}
+  virtual void cleanup()= 0;
   
   // set_thd should be called before prepare()
   void set_thd(THD *thd_arg) { thd= thd_arg; }
@@ -318,6 +322,7 @@ public:
   subselect_union_engine(st_select_lex_unit *u,
 			 select_subselect *result,
 			 Item_subselect *item);
+  void cleanup();
   int prepare();
   void fix_length_and_dec(Item_cache** row);
   int exec();
@@ -345,6 +350,7 @@ public:
     set_thd(thd_arg);
   }
   ~subselect_uniquesubquery_engine();
+  void cleanup();
   int prepare();
   void fix_length_and_dec(Item_cache** row);
   int exec();
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index e01f9db3463..87e8b124d4b 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -1084,6 +1084,7 @@ int dump_leaf(byte* key, uint32 count __attribute__((unused)),
 
 void Item_sum_count_distinct::cleanup()
 {
+  DBUG_ENTER("Item_sum_count_distinct::cleanup");
   Item_sum_int::cleanup();
   /*
     Free table and tree if they belong to this item (if item have not pointer
@@ -1099,6 +1100,7 @@ void Item_sum_count_distinct::cleanup()
     table= 0;
     use_tree= 0;
   }
+  DBUG_VOID_RETURN;
 }
 
 bool Item_sum_count_distinct::fix_fields(THD *thd, TABLE_LIST *tables,
@@ -1666,6 +1668,7 @@ Item_func_group_concat::Item_func_group_concat(bool is_distinct,
 
 void Item_func_group_concat::cleanup()
 {
+  DBUG_ENTER("Item_func_group_concat::cleanup");
   /*
     Free table and tree if they belong to this item (if item have not pointer
     to original item from which was made copy => it own its objects )
@@ -1679,6 +1682,7 @@ void Item_func_group_concat::cleanup()
     if (tree_mode)
       delete_tree(tree); 
   }
+  DBUG_VOID_RETURN;
 }
 
 Item_func_group_concat::~Item_func_group_concat()
diff --git a/sql/item_sum.h b/sql/item_sum.h
index dc84e4d4ab7..038b3ecd71e 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -60,8 +60,10 @@ public:
   Item_sum(THD *thd, Item_sum *item);
   void cleanup()
   {
+    DBUG_ENTER("Item_sum::cleanup");
     Item_result_field::cleanup();
     result_field=0;
+    DBUG_VOID_RETURN;
   }
 
   enum Type type() const { return SUM_FUNC_ITEM; }
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 7b3d1fd3cd2..cce42ad9c65 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -83,7 +83,7 @@ extern "C" void free_user_var(user_var_entry *entry)
 ** Thread specific functions
 ****************************************************************************/
 
-THD::THD():user_time(0), is_fatal_error(0),
+THD::THD():user_time(0), current_statement(0), is_fatal_error(0),
 	   last_insert_id_used(0),
 	   insert_id_used(0), rand_used(0), in_lock_tables(0),
 	   global_read_lock(0), bootstrap(0)
@@ -1232,6 +1232,21 @@ void Statement::set_statement(Statement *stmt)
   mem_root=       stmt->mem_root;
 }
 
+void Statement::set_n_backup_item_arena(Statement *set, Statement *backup)
+{
+  backup->mem_root= mem_root;
+  backup->free_list= free_list;
+  set_item_arena(set);
+}
+
+
+void Statement::set_item_arena(Statement *set)
+{
+  mem_root= set->mem_root;
+  free_list= set->free_list;
+}
+
+
 
 Statement::~Statement()
 {
diff --git a/sql/sql_class.h b/sql/sql_class.h
index 7971137d848..fbe42c9876e 100644
--- a/sql/sql_class.h
+++ b/sql/sql_class.h
@@ -427,7 +427,7 @@ class Statement
 public:
   /* FIXME: must be private */
   LEX     main_lex;
-public:
+
   /*
     Uniquely identifies each statement object in thread scope; change during
     statement lifetime. FIXME: must be const
@@ -476,7 +476,7 @@ public:
   char *query;
   uint32 query_length;                          // current query length
   /*
-    List of items created in the parser for this query. Every item puts 
+    List of items created in the parser for this query. Every item puts
     itself to the list on creation (see Item::Item() for details))
   */
   Item *free_list;
@@ -503,6 +503,15 @@ public:
   void set_statement(Statement *stmt);
   /* return class type */
   virtual Type type() const;
+
+  void set_n_backup_item_arena(Statement *set, Statement *backup);
+  inline void restore_backup_item_arena(Statement *backup)
+  {
+    set_item_arena(backup);
+    // reset backup mem_root to avoid its freeing
+    init_alloc_root(&backup->mem_root, 0, 0);
+  }
+  void set_item_arena(Statement *set);
 };
 
 
@@ -689,6 +698,10 @@ public:
   Vio* active_vio;
 #endif
   /*
+    Current prepared Statement if there one, or 0
+  */
+  Statement *current_statement;
+  /*
     next_insert_id is set on SET INSERT_ID= #. This is used as the next
     generated auto_increment value in handler.cc
   */
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 65c958093bd..b5a31ea0259 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -1561,7 +1561,11 @@ void st_select_lex::print_limit(THD *thd, String *str)
 
 /*
   There are st_select_lex::add_table_to_list & 
-  st_select_lex::set_lock_for_tables in sql_parse.cc
+  st_select_lex::set_lock_for_tables are in sql_parse.cc
 
   st_select_lex::print is in sql_select.h
+
+  st_select_lex_unit::prepare, st_select_lex_unit::exec,
+  st_select_lex_unit::cleanup, st_select_lex_unit::reinit_exec_mechanism
+  are in sql_union.cc
 */
diff --git a/sql/sql_lex.h b/sql/sql_lex.h
index 68385bc7bba..969d601649f 100644
--- a/sql/sql_lex.h
+++ b/sql/sql_lex.h
@@ -354,6 +354,7 @@ public:
   int prepare(THD *thd, select_result *result, ulong additional_options);
   int exec();
   int cleanup();
+  void reinit_exec_mechanism();
 
   void print(String *str);
 
diff --git a/sql/sql_prepare.cc b/sql/sql_prepare.cc
index de0d0c8aca8..a1c1409ca33 100644
--- a/sql/sql_prepare.cc
+++ b/sql/sql_prepare.cc
@@ -753,14 +753,21 @@ static bool mysql_test_select_fields(Prepared_statement *stmt,
       DBUG_RETURN(1);
     }
 
-    JOIN *join= new JOIN(thd, fields, select_options, result);
     thd->used_tables= 0;	// Updated by setup_fields  
-
-    if (join->prepare(&select_lex->ref_pointer_array,
-		      (TABLE_LIST*)select_lex->get_table_list(),
-                      wild_num, conds, og_num, order, group, having, proc, 
-                      select_lex, unit))
+    Statement backup;
+    /*
+      we do not want to have in statement memory all that junk,
+      which will be created by preparation => substitute memory
+      from original thread pool
+    */
+    thd->set_n_backup_item_arena(&thd->stmt_backup, &backup);
+    if ((unit->prepare(thd, result, 0)))
+    {
+      thd->restore_backup_item_arena(&backup);
       DBUG_RETURN(1);
+    }
+    thd->restore_backup_item_arena(&backup);
+   
     if (send_prep_stmt(stmt, fields.elements) ||
         thd->protocol_simple.send_fields(&fields, 0)
 #ifndef EMBEDDED_LIBRARY
@@ -768,7 +775,7 @@ static bool mysql_test_select_fields(Prepared_statement *stmt,
 #endif
        )
       DBUG_RETURN(1);
-    join->cleanup();
+    unit->cleanup();
   }
   DBUG_RETURN(0);  
 }
@@ -899,6 +906,7 @@ bool mysql_stmt_prepare(THD *thd, char *packet, uint packet_length)
 
   thd->stmt_backup.set_statement(thd);
   thd->set_statement(stmt);
+  thd->current_statement= stmt;
 
   if (alloc_query(thd, packet, packet_length))
     goto alloc_query_err;
@@ -929,6 +937,7 @@ bool mysql_stmt_prepare(THD *thd, char *packet, uint packet_length)
   cleanup_items(thd->free_list);
   stmt->set_statement(thd);
   thd->set_statement(&thd->stmt_backup);
+  thd->current_statement= 0;
 
   if (init_param_items(stmt))
     goto init_param_err;
@@ -947,6 +956,7 @@ alloc_query_err:
   thd->stmt_map.erase(stmt);
   DBUG_RETURN(1);
 insert_stmt_err:
+  thd->current_statement= 0;
   delete stmt;
   DBUG_RETURN(1);
 }
@@ -980,6 +990,7 @@ void mysql_stmt_execute(THD *thd, char *packet)
   stmt->query_id= thd->query_id;
   thd->stmt_backup.set_statement(thd);
   thd->set_statement(stmt);
+  thd->current_statement= stmt;
   thd->free_list= 0;
 
   /*
@@ -1009,17 +1020,21 @@ void mysql_stmt_execute(THD *thd, char *packet)
       order->item= (Item **)(order+1);
     for (order=(ORDER *)sl->order_list.first ; order ; order=order->next)
       order->item= (Item **)(order+1);
+
+    /*
+      TODO: When the new table structure is ready, then have a status bit 
+      to indicate the table is altered, and re-do the setup_* 
+      and open the tables back.
+    */
+    for (TABLE_LIST *tables= (TABLE_LIST*) sl->table_list.first;
+	 tables;
+	 tables= tables->next)
+    {
+      tables->table= 0; // safety - nasty init
+      tables->table_list= 0;
+    }
   }
 
-  /*
-    TODO: When the new table structure is ready, then have a status bit 
-    to indicate the table is altered, and re-do the setup_* 
-    and open the tables back.
-  */
-  for (TABLE_LIST *tables= (TABLE_LIST*) stmt->lex->select_lex.table_list.first;
-       tables;
-       tables= tables->next)
-    tables->table= 0; // safety - nasty init
 
 #ifndef EMBEDDED_LIBRARY
   if (stmt->param_count && setup_params_data(stmt))
@@ -1049,6 +1064,7 @@ void mysql_stmt_execute(THD *thd, char *packet)
   cleanup_items(stmt->free_list);
   free_root(&thd->mem_root, MYF(0));
   thd->set_statement(&thd->stmt_backup);
+  thd->current_statement= 0;
   DBUG_VOID_RETURN;
 }
 
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index ad5799f4c42..e5cb306c81b 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -330,8 +330,7 @@ JOIN::prepare(Item ***rref_pointer_array,
   // Is it subselect
   {
     Item_subselect *subselect;
-    if ((subselect= select_lex->master_unit()->item) &&
-	select_lex->linkage != GLOBAL_OPTIONS_TYPE)
+    if ((subselect= select_lex->master_unit()->item))
     {
       Item_subselect::trans_res res;
       if ((res= subselect->select_transformer(this)) !=
@@ -1527,10 +1526,10 @@ JOIN::cleanup()
 
   lock=0;                                     // It's faster to unlock later
   join_free(1);
-   if (exec_tmp_table1)
-     free_tmp_table(thd, exec_tmp_table1);
-   if (exec_tmp_table2)
-     free_tmp_table(thd, exec_tmp_table2);
+  if (exec_tmp_table1)
+    free_tmp_table(thd, exec_tmp_table1);
+  if (exec_tmp_table2)
+    free_tmp_table(thd, exec_tmp_table2);
   delete select;
   delete_dynamic(&keyuse);
   delete procedure;
diff --git a/sql/sql_union.cc b/sql/sql_union.cc
index 226086d0d24..a7719a3b519 100644
--- a/sql/sql_union.cc
+++ b/sql/sql_union.cc
@@ -468,3 +468,9 @@ int st_select_lex_unit::cleanup()
   }
   DBUG_RETURN(error);
 }
+
+
+void st_select_lex_unit::reinit_exec_mechanism()
+{
+  prepared= optimized= executed= 0;
+}
diff --git a/tests/client_test.c b/tests/client_test.c
index 66637dcb04b..fbc9322b6b7 100644
--- a/tests/client_test.c
+++ b/tests/client_test.c
@@ -8095,6 +8095,53 @@ static void test_bug1946()
   rc= mysql_query(mysql,"DROP TABLE prepare_command");
 }
 
+static void test_subqueries()
+{
+  MYSQL_STMT *stmt;
+  int rc, i;
+  const char *query= "SELECT (SELECT SUM(a+b) FROM t2 where t1.b=t2.b GROUP BY t1.a LIMIT 1) as scalar_s, exists (select 1 from t2 where t2.a/2=t1.a) as exists_s, a in (select a+3 from t2) as in_s, (a-1,b-1) in (select a,b from t2) as in_row_s FROM t1";
+
+  myheader("test_subquery");
+  
+  rc = mysql_query(mysql, "DROP TABLE IF EXISTS t1,t2");
+  myquery(rc);
+  
+  rc= mysql_query(mysql,"CREATE TABLE t1 (a int , b int);");
+  myquery(rc);
+
+  rc= mysql_query(mysql,
+		  "insert into t1 values (1,1), (2, 2), (3,3), (4,4), (5,5);");
+  myquery(rc);
+
+  rc= mysql_query(mysql,"create table t2 select * from t1;");
+  myquery(rc);
+
+  stmt= mysql_prepare(mysql, query, strlen(query));
+  for (i= 0; i < 3; i++)
+  {
+    rc= mysql_execute(stmt);
+    mystmt(stmt, rc);
+    assert(5 == my_process_stmt_result(stmt));
+  }
+  mysql_stmt_close(stmt);
+
+  rc= mysql_query(mysql, "DROP TABLE t1,t2");
+  myquery(rc);
+}
+
+
+static void test_bad_union()
+{
+  MYSQL_STMT *stmt;
+  const char *query= "SELECT 1, 2 union SELECT 1";
+
+  myheader("test_bad_union");
+  
+  stmt= mysql_prepare(mysql, query, strlen(query));
+  assert(stmt == 0);
+  myerror(NULL); 
+}
+
 
 /*
   Read and parse arguments and MySQL options from my.cnf
@@ -8234,6 +8281,7 @@ int main(int argc, char **argv)
     test_count= 1;
    
     start_time= time((time_t *)0);
+
     client_query();         /* simple client query test */
 #if NOT_YET_WORKING
     /* Used for internal new development debugging */
@@ -8340,6 +8388,9 @@ int main(int argc, char **argv)
     test_bug1644();	    /* BUG#1644 */
     test_bug1946();         /* test that placeholders are allowed only in 
                                prepared queries */
+    test_subqueries();	    /* repeatable subqueries */
+    test_bad_union();       /* correct setup of UNION */
+
 
     end_time= time((time_t *)0);
     total_time+= difftime(end_time, start_time);