mariadb/sql/item_subselect.cc

/* Copyright (C) 2000 MySQL AB

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/*
   subselect Item

SUBSELECT TODO:
   - add function from mysql_select that use JOIN* as parameter to JOIN methods
     (sql_select.h/sql_select.cc)
*/

#ifdef __GNUC__
#pragma implementation				// gcc: Class implementation
#endif

#include "mysql_priv.h"
#include "sql_select.h"

inline Item * and_items(Item* cond, Item *item)
{
  return (cond? (new Item_cond_and(cond, item)) : item);
}

Item_subselect::Item_subselect():
  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();
  /*
    item value is NULL if select_subselect not changed this value
    (i.e. some rows will be found returned)
  */
  null_value= 1;
}


void Item_subselect::init(st_select_lex *select_lex,
			  select_subselect *result)
{

  DBUG_ENTER("Item_subselect::init");
  DBUG_PRINT("subs", ("select_lex 0x%xl", (ulong) select_lex));
  unit= select_lex->master_unit();

  if (unit->item)
  {
    /*
      Item can be changed in JOIN::prepare while engine in JOIN::optimize
      => we do not copy old_engine here
    */
    engine= unit->item->engine;
    parsing_place= unit->item->parsing_place;
    unit->item->engine= 0;
    unit->item= this;
    engine->change_result(this, result);
  }
  else
  {
    SELECT_LEX *outer_select= unit->outer_select();
    /*
      do not take into account expression inside aggregate functions because
      they can access original table fields
    */
    parsing_place= (outer_select->in_sum_expr ?
                    NO_MATTER :
                    outer_select->parsing_place);
    if (select_lex->next_select())
      engine= new subselect_union_engine(unit, result, this);
    else
      engine= new subselect_single_select_engine(select_lex, result, this);
  }
  {
    SELECT_LEX *upper= unit->outer_select();
    if (upper->parsing_place == IN_HAVING)
      upper->subquery_in_having= 1;
  }
  DBUG_VOID_RETURN;
}

void Item_subselect::cleanup()
{
  DBUG_ENTER("Item_subselect::cleanup");
  Item_result_field::cleanup();
  if (old_engine)
  {
    if (engine)
      engine->cleanup();
    engine= old_engine;
    old_engine= 0;
  }
  if (engine)
    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()
{
  delete engine;
}

Item_subselect::trans_res
Item_subselect::select_transformer(JOIN *join)
{
  DBUG_ENTER("Item_subselect::select_transformer");
  DBUG_RETURN(RES_OK);
}


bool Item_subselect::fix_fields(THD *thd_param, TABLE_LIST *tables, Item **ref)
{
  char const *save_where= thd_param->where;
  bool res;

  DBUG_ASSERT(fixed == 0);
  engine->set_thd((thd= thd_param));

  if (check_stack_overrun(thd, (gptr)&res))
    return TRUE;

  res= engine->prepare();

  // all transformetion is done (used by prepared statements)
  changed= 1;

  if (!res)
  {
    if (substitution)
    {
      int ret= 0;

      // 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)
	engine->exclude();
      substitution= 0;
      thd->where= "checking transformed subquery";
      if (!(*ref)->fixed)
	ret= (*ref)->fix_fields(thd, tables, ref);
      thd->where= save_where;
      return ret;
    }
    // Is it one field subselect?
    if (engine->cols() > max_columns)
    {
      my_error(ER_OPERAND_COLUMNS, MYF(0), 1);
      return TRUE;
    }
    fix_length_and_dec();
  }
  uint8 uncacheable= engine->uncacheable();
  if (uncacheable)
  {
    const_item_cache= 0;
    if (uncacheable & UNCACHEABLE_RAND)
      used_tables_cache|= RAND_TABLE_BIT;
  }
  fixed= 1;
  thd->where= save_where;
  return res;
}

bool Item_subselect::exec()
{
  int res;
  MEM_ROOT *old_root= thd->mem_root;

  /*
    As this is execution, all objects should be allocated through the main
    mem root
  */
  thd->mem_root= &thd->main_mem_root;
  res= engine->exec();
  thd->mem_root= old_root;

  if (engine_changed)
  {
    engine_changed= 0;
    return exec();
  }
  return (res);
}

Item::Type Item_subselect::type() const
{
  return SUBSELECT_ITEM;
}


void Item_subselect::fix_length_and_dec()
{
  engine->fix_length_and_dec(0);
}


table_map Item_subselect::used_tables() const
{
  return (table_map) (engine->uncacheable() ? used_tables_cache : 0L);
}


bool Item_subselect::const_item() const
{
  return const_item_cache;
}

Item *Item_subselect::get_tmp_table_item(THD *thd)
{
  if (!with_sum_func && !const_item())
    return new Item_field(result_field);
  return copy_or_same(thd);
}

void Item_subselect::update_used_tables()
{
  if (!engine->uncacheable())
  {
    // did all used tables become ststic?
    if (!(used_tables_cache & ~engine->upper_select_const_tables()))
      const_item_cache= 1;
  }
}


void Item_subselect::print(String *str)
{
  str->append('(');
  engine->print(str);
  str->append(')');
}


Item_singlerow_subselect::Item_singlerow_subselect(st_select_lex *select_lex)
  :Item_subselect(), value(0)
{
  DBUG_ENTER("Item_singlerow_subselect::Item_singlerow_subselect");
  init(select_lex, new select_singlerow_subselect(this));
  max_columns= 1;
  maybe_null= 1;
  max_columns= UINT_MAX;
  DBUG_VOID_RETURN;
}

Item_maxmin_subselect::Item_maxmin_subselect(THD *thd_param,
                                             Item_subselect *parent,
					     st_select_lex *select_lex,
					     bool max_arg)
  :Item_singlerow_subselect()
{
  DBUG_ENTER("Item_maxmin_subselect::Item_maxmin_subselect");
  max= max_arg;
  init(select_lex, new select_max_min_finder_subselect(this, max_arg));
  max_columns= 1;
  maybe_null= 1;
  max_columns= 1;

  /*
    Following information was collected during performing fix_fields()
    of Items belonged to subquery, which will be not repeated
  */
  used_tables_cache= parent->get_used_tables_cache();
  const_item_cache= parent->get_const_item_cache();

  /*
    this subquery alwais creates during preparation, so we can assign
    thd here
  */
  thd= thd_param;

  DBUG_VOID_RETURN;
}

void Item_maxmin_subselect::print(String *str)
{
  str->append(max?"<max>":"<min>", 5);
  Item_singlerow_subselect::print(str);
}

void Item_singlerow_subselect::reset()
{
  null_value= 1;
  if (value)
    value->null_value= 1;
}

Item_subselect::trans_res
Item_singlerow_subselect::select_transformer(JOIN *join)
{
  if (changed)
    return RES_OK;

  SELECT_LEX *select_lex= join->select_lex;
  Item_arena *arena= thd->current_arena;
 
  if (!select_lex->master_unit()->first_select()->next_select() &&
      !select_lex->table_list.elements &&
      select_lex->item_list.elements == 1 &&
      !select_lex->item_list.head()->with_sum_func &&
      /*
	We cant change name of Item_field or Item_ref, because it will
	prevent it's correct resolving, but we should save name of
	removed item => we do not make optimization if top item of
	list is field or reference.
	TODO: solve above problem
      */
      !(select_lex->item_list.head()->type() == FIELD_ITEM ||
	select_lex->item_list.head()->type() == REF_ITEM) &&
      /*
        switch off this optimisation for prepare statement,
        because we do not rollback this changes
        TODO: make rollback for it, or special name resolving mode in 5.0.
      */
      !arena->is_stmt_prepare()
      )
  {

    have_to_be_excluded= 1;
    if (thd->lex->describe)
    {
      char warn_buff[MYSQL_ERRMSG_SIZE];
      sprintf(warn_buff, ER(ER_SELECT_REDUCED), select_lex->select_number);
      push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
		   ER_SELECT_REDUCED, warn_buff);
    }
    substitution= select_lex->item_list.head();
    /*
      as far as we moved content to upper leven, field which depend of
      'upper' select is not really dependent => we remove this dependence
    */
    substitution->walk(&Item::remove_dependence_processor,
		       (byte *) select_lex->outer_select());
    if (join->conds || join->having)
    {
      Item *cond;
      if (!join->having)
	cond= join->conds;
      else if (!join->conds)
	cond= join->having;
      else
	if (!(cond= new Item_cond_and(join->conds, join->having)))
	  goto err;
      if (!(substitution= new Item_func_if(cond, substitution,
					   new Item_null())))
	goto err;
    }
    return RES_REDUCE;
  }
  return RES_OK;

err:
  return RES_ERROR;
}


void Item_singlerow_subselect::store(uint i, Item *item)
{
  row[i]->store(item);
}

enum Item_result Item_singlerow_subselect::result_type() const
{
  return engine->type();
}

void Item_singlerow_subselect::fix_length_and_dec()
{
  if ((max_columns= engine->cols()) == 1)
  {
    engine->fix_length_and_dec(row= &value);
  }
  else
  {
    if (!(row= (Item_cache**) sql_alloc(sizeof(Item_cache*)*max_columns)))
      return;
    engine->fix_length_and_dec(row);
    value= *row;
  }
  /*
    If there are not tables in subquery then ability to have NULL value
    depends on SELECT list (if single row subquery have tables then it
    always can be NULL if there are not records fetched).
  */
  if (engine->no_tables())
    maybe_null= engine->may_be_null();
}

uint Item_singlerow_subselect::cols()
{
  return engine->cols();
}

bool Item_singlerow_subselect::check_cols(uint c)
{
  if (c != engine->cols())
  {
    my_error(ER_OPERAND_COLUMNS, MYF(0), c);
    return 1;
  }
  return 0;
}

bool Item_singlerow_subselect::null_inside()
{
  for (uint i= 0; i < max_columns ; i++)
  {
    if (row[i]->null_value)
      return 1;
  }
  return 0;
}

void Item_singlerow_subselect::bring_value()
{
  exec();
}

double Item_singlerow_subselect::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (!exec() && !value->null_value)
  {
    null_value= 0;
    return value->val_real();
  }
  else
  {
    reset();
    return 0;
  }
}

longlong Item_singlerow_subselect::val_int()
{
  DBUG_ASSERT(fixed == 1);
  if (!exec() && !value->null_value)
  {
    null_value= 0;
    return value->val_int();
  }
  else
  {
    reset();
    return 0;
  }
}

String *Item_singlerow_subselect::val_str (String *str)
{
  if (!exec() && !value->null_value)
  {
    null_value= 0;
    return value->val_str(str);
  }
  else
  {
    reset();
    return 0;
  }
}


Item_exists_subselect::Item_exists_subselect(st_select_lex *select_lex):
  Item_subselect()
{
  DBUG_ENTER("Item_exists_subselect::Item_exists_subselect");
  init(select_lex, new select_exists_subselect(this));
  max_columns= UINT_MAX;
  null_value= 0; //can't be NULL
  maybe_null= 0; //can't be NULL
  value= 0;
  // We need only 1 row to determinate existence
  select_lex->master_unit()->global_parameters->select_limit= 1;
  DBUG_VOID_RETURN;
}


void Item_exists_subselect::print(String *str)
{
  str->append("exists", 6);
  Item_subselect::print(str);
}


bool Item_in_subselect::test_limit(SELECT_LEX_UNIT *unit)
{
  if (unit->fake_select_lex &&
      unit->fake_select_lex->test_limit())
    return(1);

  SELECT_LEX *sl= unit->first_select();
  for (; sl; sl= sl->next_select())
  {
    if (sl->test_limit())
      return(1);
  }
  return(0);
}

Item_in_subselect::Item_in_subselect(Item * left_exp,
				     st_select_lex *select_lex):
  Item_exists_subselect(), transformed(0), upper_not(0)
{
  DBUG_ENTER("Item_in_subselect::Item_in_subselect");
  left_expr= left_exp;
  init(select_lex, new select_exists_subselect(this));
  max_columns= UINT_MAX;
  maybe_null= 1;
  abort_on_null= 0;
  reset();
  //if test_limit will fail then error will be reported to client
  test_limit(select_lex->master_unit());
  DBUG_VOID_RETURN;
}

Item_allany_subselect::Item_allany_subselect(Item * left_exp,
					     Comp_creator *fn,
					     st_select_lex *select_lex,
					     bool all_arg)
  :Item_in_subselect(), all(all_arg)
{
  DBUG_ENTER("Item_in_subselect::Item_in_subselect");
  left_expr= left_exp;
  func= fn;
  init(select_lex, new select_exists_subselect(this));
  max_columns= 1;
  abort_on_null= 0;
  reset();
  //if test_limit will fail then error will be reported to client
  test_limit(select_lex->master_unit());
  DBUG_VOID_RETURN;
}


void Item_exists_subselect::fix_length_and_dec()
{
   decimals= 0;
   max_length= 1;
   max_columns= engine->cols();
}

double Item_exists_subselect::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (exec())
  {
    reset();
    return 0;
  }
  return (double) value;
}

longlong Item_exists_subselect::val_int()
{
  DBUG_ASSERT(fixed == 1);
  if (exec())
  {
    reset();
    return 0;
  }
  return value;
}

String *Item_exists_subselect::val_str(String *str)
{
  DBUG_ASSERT(fixed == 1);
  if (exec())
  {
    reset();
    return 0;
  }
  str->set(value,&my_charset_bin);
  return str;
}

double Item_in_subselect::val_real()
{
  DBUG_ASSERT(fixed == 1);
  if (exec())
  {
    reset();
    null_value= 1;
    return 0;
  }
  if (was_null && !value)
    null_value= 1;
  return (double) value;
}

longlong Item_in_subselect::val_int()
{
  DBUG_ASSERT(fixed == 1);
  if (exec())
  {
    reset();
    null_value= 1;
    return 0;
  }
  if (was_null && !value)
    null_value= 1;
  return value;
}

String *Item_in_subselect::val_str(String *str)
{
  DBUG_ASSERT(fixed == 1);
  if (exec())
  {
    reset();
    null_value= 1;
    return 0;
  }
  if (was_null && !value)
  {
    null_value= 1;
    return 0;
  }
  str->set(value, &my_charset_bin);
  return str;
}


/* Rewrite a single-column IN/ALL/ANY subselect. */

Item_subselect::trans_res
Item_in_subselect::single_value_transformer(JOIN *join,
					    Comp_creator *func)
{
  const char *save_where= thd->where;
  Item_subselect::trans_res result= RES_ERROR;
  DBUG_ENTER("Item_in_subselect::single_value_transformer");

  if (changed)
  {
    DBUG_RETURN(RES_OK);
  }

  SELECT_LEX *select_lex= join->select_lex;
  Item_arena *arena, backup;
  arena= thd->change_arena_if_needed(&backup);
  thd->where= "scalar IN/ALL/ANY subquery";

  /*
    Check that the right part of the subselect contains no more than one
    column. E.g. in SELECT 1 IN (SELECT * ..) the right part is (SELECT * ...)
  */
  if (select_lex->item_list.elements > 1)
  {
    my_error(ER_OPERAND_COLUMNS, MYF(0), 1);
    goto err;
  }

  /*
    If this is an ALL/ANY single-value subselect, try to rewrite it with
    a MIN/MAX subselect. We can do that if a possible NULL result of the
    subselect can be ignored.
    E.g. SELECT * FROM t1 WHERE b > ANY (SELECT a FROM t2) can be rewritten
    with SELECT * FROM t1 WHERE b > (SELECT MAX(a) FROM t2).
    We can't check that this optimization is safe if it's not a top-level
    item of the WHERE clause (e.g. because the WHERE clause can contain IS
    NULL/IS NOT NULL functions). If so, we rewrite ALL/ANY with NOT EXISTS
    later in this method.
  */
  if ((abort_on_null || (upper_not && upper_not->top_level())) &&
      !select_lex->master_unit()->uncacheable && !func->eqne_op())
  {
    if (substitution)
    {
      // It is second (third, ...) SELECT of UNION => All is done
      goto ok;
    }

    Item *subs;
    if (!select_lex->group_list.elements &&
	!select_lex->with_sum_func &&
	!(select_lex->next_select()))
    {
      Item *item;
      if (func->l_op())
      {
	/*
	  (ALL && (> || =>)) || (ANY && (< || =<))
	  for ALL condition is inverted
	*/
	item= new Item_sum_max(*select_lex->ref_pointer_array);
      }
      else
      {
	/*
	  (ALL && (< || =<)) || (ANY && (> || =>))
	  for ALL condition is inverted
	*/
	item= new Item_sum_min(*select_lex->ref_pointer_array);
      }
      *select_lex->ref_pointer_array= item;
      {
	List_iterator<Item> it(select_lex->item_list);
	it++;
	it.replace(item);
      }

      /*
	Item_sum_(max|min) can't substitute other item => we can use 0 as
	reference
      */
      if (item->fix_fields(thd, join->tables_list, 0))
	goto err;
      /* we added aggregate function => we have to change statistic */
      count_field_types(&join->tmp_table_param, join->all_fields, 0);

      subs= new Item_singlerow_subselect(select_lex);
    }
    else
    {
      // remove LIMIT placed  by ALL/ANY subquery
      select_lex->master_unit()->global_parameters->select_limit=
	HA_POS_ERROR;
      subs= new Item_maxmin_subselect(thd, this, select_lex, func->l_op());
    }
    // left expression belong to outer select
    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->lex->current_select= current;
      goto err;
    }
    thd->lex->current_select= current;
    substitution= func->create(left_expr, subs);
    goto ok;
  }

  if (!substitution)
  {
    //first call for this unit
    SELECT_LEX_UNIT *unit= select_lex->master_unit();
    substitution= optimizer= new Item_in_optimizer(left_expr, this);

    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, up->get_table_list(), 0))
    {
      thd->lex->current_select= current;
      goto err;
    }
    thd->lex->current_select= current;

    /*
      As far as  Item_ref_in_optimizer do not substitude itself on fix_fields
      we can use same item for all selects.
    */
    expr= new Item_ref((Item**)optimizer->get_cache(),
		       (char *)"<no matter>",
		       (char *)in_left_expr_name);

    unit->uncacheable|= UNCACHEABLE_DEPENDENT;
  }

  select_lex->uncacheable|= UNCACHEABLE_DEPENDENT;
  /*
    Add the left part of a subselect to a WHERE or HAVING clause of
    the right part, e.g. SELECT 1 IN (SELECT a FROM t1)  =>
    SELECT Item_in_optimizer(1, SELECT a FROM t1 WHERE a=1)
    HAVING is used only if the right part contains a SUM function, a GROUP
    BY or a HAVING clause.
  */
  if (join->having || select_lex->with_sum_func ||
      select_lex->group_list.elements)
  {
    bool tmp;
    Item *item= func->create(expr,
                             new Item_ref_null_helper(this,
                                                      select_lex->
                                                      ref_pointer_array,
                                                      (char *)"<ref>",
                                                      this->full_name()));
    /*
      AND and comparison functions can't be changed during fix_fields()
      we can assign select_lex->having here, and pass 0 as last
      argument (reference) to fix_fields()
    */
    select_lex->having= join->having= and_items(join->having, item);
    select_lex->having_fix_field= 1;
    tmp= join->having->fix_fields(thd, join->tables_list, 0);
    select_lex->having_fix_field= 0;
    if (tmp)
      goto err;
  }
  else
  {
    Item *item= (Item*) select_lex->item_list.head();

    select_lex->item_list.empty();
    select_lex->item_list.push_back(new Item_int("Not_used",
						 (longlong) 1, 21));
    select_lex->ref_pointer_array[0]= select_lex->item_list.head();
    if (select_lex->table_list.elements)
    {
      bool tmp;
      Item *having= item, *orig_item= item;
      item= func->create(expr, item);
      if (!abort_on_null && orig_item->maybe_null)
      {
	having= new Item_is_not_null_test(this, having);
	/*
	  Item_is_not_null_test can't be changed during fix_fields()
	  we can assign select_lex->having here, and pass 0 as last
	  argument (reference) to fix_fields()
	*/
	select_lex->having=
	  join->having= (join->having ?
			 new Item_cond_and(having, join->having) :
			 having);
	select_lex->having_fix_field= 1;
	tmp= join->having->fix_fields(thd, join->tables_list, 0);
        select_lex->having_fix_field= 0;
        if (tmp)
	  goto err;
	item= new Item_cond_or(item,
			       new Item_func_isnull(orig_item));
      }
      item->name= (char *)in_additional_cond;
      /*
	AND can't be changed during fix_fields()
	we can assign select_lex->having here, and pass 0 as last
	argument (reference) to fix_fields()
      */
      select_lex->where= join->conds= and_items(join->conds, item);
      if (join->conds->fix_fields(thd, join->tables_list, 0))
	goto err;
    }
    else
    {
      bool tmp;
      if (select_lex->master_unit()->first_select()->next_select())
      {
	/*
	  comparison functions can't be changed during fix_fields()
	  we can assign select_lex->having here, and pass 0 as last
	  argument (reference) to fix_fields()
	*/
	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;
	tmp= join->having->fix_fields(thd, join->tables_list, 0);
        select_lex->having_fix_field= 0;
        if (tmp)
	  goto err;
      }
      else
      {
	// it is single select without tables => possible optimization
	item= func->create(left_expr, item);
	// fix_field of item will be done in time of substituting
	substitution= item;
	have_to_be_excluded= 1;
	if (thd->lex->describe)
	{
	  char warn_buff[MYSQL_ERRMSG_SIZE];
	  sprintf(warn_buff, ER(ER_SELECT_REDUCED), select_lex->select_number);
	  push_warning(thd, MYSQL_ERROR::WARN_LEVEL_NOTE,
		       ER_SELECT_REDUCED, warn_buff);
	}
        result= RES_REDUCE;
        goto err;
      }
    }
  }

ok:
  thd->where= save_where;
  result= RES_OK;

err:
  if (arena)
    thd->restore_backup_item_arena(arena, &backup);
  DBUG_RETURN(result);
}


Item_subselect::trans_res
Item_in_subselect::row_value_transformer(JOIN *join)
{
  const char *save_where= thd->where;
  Item *item= 0;
  SELECT_LEX *select_lex= join->select_lex;
  DBUG_ENTER("Item_in_subselect::row_value_transformer");

  if (changed)
  {
    DBUG_RETURN(RES_OK);
  }
  thd->where= "row IN/ALL/ANY subquery";

  Item_arena *arena, backup;
  arena= thd->change_arena_if_needed(&backup);

  if (select_lex->item_list.elements != left_expr->cols())
  {
    my_error(ER_OPERAND_COLUMNS, MYF(0), left_expr->cols());
    goto err;
  }

  if (!substitution)
  {
    //first call for this unit
    SELECT_LEX_UNIT *unit= select_lex->master_unit();
    substitution= optimizer= new Item_in_optimizer(left_expr, this);

    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, up->get_table_list(), 0))
    {
      thd->lex->current_select= current;
      goto err;
    }

    // we will refer to apper level cache array => we have to save it in PS
    optimizer->keep_top_level_cache();

    thd->lex->current_select= current;
    unit->uncacheable|= UNCACHEABLE_DEPENDENT;
  }

  select_lex->uncacheable|= UNCACHEABLE_DEPENDENT;
  {
    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),
				       (char *)"<no matter>",
				     (char *)in_left_expr_name),
			  func);
      item= and_items(item, func);
    }
  }
  if (join->having || select_lex->with_sum_func ||
      select_lex->group_list.first ||
      !select_lex->table_list.elements)
  {
    /*
      AND can't be changed during fix_fields()
      we can assign select_lex->having here, and pass 0 as last
      argument (reference) to fix_fields()
    */
    select_lex->having= join->having= and_items(join->having, item);
    select_lex->having_fix_field= 1;
    if (join->having->fix_fields(thd, join->tables_list, 0))
    {
      select_lex->having_fix_field= 0;
      goto err;
    }
    select_lex->having_fix_field= 0;
  }
  else
  {
    /*
      AND can't be changed during fix_fields()
      we can assign select_lex->having here, and pass 0 as last
      argument (reference) to fix_fields()
    */
    select_lex->where= join->conds= and_items(join->conds, item);
    if (join->conds->fix_fields(thd, join->tables_list, 0))
      goto err;
  }
  thd->where= save_where;
  if (arena)
    thd->restore_backup_item_arena(arena, &backup);
  DBUG_RETURN(RES_OK);

err:
  if (arena)
    thd->restore_backup_item_arena(arena, &backup);
  DBUG_RETURN(RES_ERROR);
}


Item_subselect::trans_res
Item_in_subselect::select_transformer(JOIN *join)
{
  transformed= 1;
  if (left_expr->cols() == 1)
    return single_value_transformer(join, &eq_creator);
  return row_value_transformer(join);
}


void Item_in_subselect::print(String *str)
{
  if (transformed)
    str->append("<exists>", 8);
  else
  {
    left_expr->print(str);
    str->append(" in ", 4);
  }
  Item_subselect::print(str);
}


Item_subselect::trans_res
Item_allany_subselect::select_transformer(JOIN *join)
{
  transformed= 1;
  if (upper_not)
    upper_not->show= 1;
  return single_value_transformer(join, func);
}


void Item_allany_subselect::print(String *str)
{
  if (transformed)
    str->append("<exists>", 8);
  else
  {
    left_expr->print(str);
    str->append(' ');
    str->append(func->symbol(all));
    str->append(all ? " all " : " any ", 5);
  }
  Item_subselect::print(str);
}


subselect_single_select_engine::
subselect_single_select_engine(st_select_lex *select,
			       select_subselect *result,
			       Item_subselect *item)
  :subselect_engine(item, result),
   prepared(0), optimized(0), executed(0), join(0)
{
  select_lex= select;
  SELECT_LEX_UNIT *unit= select_lex->master_unit();
  unit->set_limit(unit->global_parameters, select_lex);
  unit->item= item;
  this->select_lex= select_lex;
}


void subselect_single_select_engine::cleanup()
{
  DBUG_ENTER("subselect_single_select_engine::cleanup");
  prepared= optimized= executed= 0;
  join= 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)
  :subselect_engine(item_arg, result_arg)
{
  unit= u;
  if (!result_arg)				//out of memory
    current_thd->fatal_error();
  unit->item= item_arg;
}


int subselect_single_select_engine::prepare()
{
  if (prepared)
    return 0;
  join= new JOIN(thd, select_lex->item_list,
		 select_lex->options | SELECT_NO_UNLOCK, result);
  if (!join || !result)
  {
    thd->fatal_error();				//out of memory
    return 1;
  }
  prepared= 1;
  SELECT_LEX *save_select= thd->lex->current_select;
  thd->lex->current_select= select_lex;
  if (join->prepare(&select_lex->ref_pointer_array,
		    (TABLE_LIST*) select_lex->table_list.first,
		    select_lex->with_wild,
		    select_lex->where,
		    select_lex->order_list.elements +
		    select_lex->group_list.elements,
		    (ORDER*) select_lex->order_list.first,
		    (ORDER*) select_lex->group_list.first,
		    select_lex->having,
		    (ORDER*) 0, select_lex,
		    select_lex->master_unit()))
    return 1;
  thd->lex->current_select= save_select;
  return 0;
}

int subselect_union_engine::prepare()
{
  return unit->prepare(thd, result, SELECT_NO_UNLOCK);
}

int subselect_uniquesubquery_engine::prepare()
{
  //this never should be called
  DBUG_ASSERT(0);
  return 1;
}

static Item_result set_row(List<Item> &item_list, Item *item,
			   Item_cache **row, bool *maybe_null)
{
  Item_result res_type= STRING_RESULT;
  Item *sel_item;
  List_iterator_fast<Item> li(item_list);
  for (uint i= 0; (sel_item= li++); i++)
  {
    item->max_length= sel_item->max_length;
    res_type= sel_item->result_type();
    item->decimals= sel_item->decimals;
    *maybe_null= sel_item->maybe_null;
    if (!(row[i]= Item_cache::get_cache(res_type)))
      return STRING_RESULT; // we should return something
    row[i]->setup(sel_item);
  }
  if (item_list.elements > 1)
    res_type= ROW_RESULT;
  return res_type;
}

void subselect_single_select_engine::fix_length_and_dec(Item_cache **row)
{
  DBUG_ASSERT(row || select_lex->item_list.elements==1);
  res_type= set_row(select_lex->item_list, item, row, &maybe_null);
  item->collation.set(row[0]->collation);
  if (cols() != 1)
    maybe_null= 0;
}

void subselect_union_engine::fix_length_and_dec(Item_cache **row)
{
  DBUG_ASSERT(row || unit->first_select()->item_list.elements==1);

  if (unit->first_select()->item_list.elements == 1)
  {
    res_type= set_row(unit->types, item, row, &maybe_null);
    item->collation.set(row[0]->collation);
  }
  else
  {
    bool fake= 0;
    res_type= set_row(unit->types, item, row, &fake);
  }
}

void subselect_uniquesubquery_engine::fix_length_and_dec(Item_cache **row)
{
  //this never should be called
  DBUG_ASSERT(0);
}

int subselect_single_select_engine::exec()
{
  DBUG_ENTER("subselect_single_select_engine::exec");
  char const *save_where= thd->where;
  SELECT_LEX *save_select= thd->lex->current_select;
  thd->lex->current_select= select_lex;
  if (!optimized)
  {
    optimized=1;
    if (join->optimize())
    {
      thd->where= save_where;
      executed= 1;
      thd->lex->current_select= save_select;
      DBUG_RETURN(join->error ? join->error : 1);
    }
    if (item->engine_changed)
    {
      DBUG_RETURN(1);
    }
  }
  if (select_lex->uncacheable && executed)
  {
    if (join->reinit())
    {
      thd->where= save_where;
      thd->lex->current_select= save_select;
      DBUG_RETURN(1);
    }
    item->reset();
    item->assigned((executed= 0));
  }
  if (!executed)
  {
    join->exec();
    executed= 1;
    thd->where= save_where;
    thd->lex->current_select= save_select;
    DBUG_RETURN(join->error||thd->is_fatal_error);
  }
  thd->where= save_where;
  thd->lex->current_select= save_select;
  DBUG_RETURN(0);
}

int subselect_union_engine::exec()
{
  char const *save_where= thd->where;
  int res= unit->exec();
  thd->where= save_where;
  return res;
}


int subselect_uniquesubquery_engine::exec()
{
  DBUG_ENTER("subselect_uniquesubquery_engine::exec");
  int error;
  TABLE *table= tab->table;
  for (store_key **copy=tab->ref.key_copy ; *copy ; copy++)
  {
    if (tab->ref.key_err= (*copy)->copy())
    {
      table->status= STATUS_NOT_FOUND;
      DBUG_RETURN(1);
    }
  }

  if (!table->file->inited)
    table->file->ha_index_init(tab->ref.key);
  error= table->file->index_read(table->record[0],
                                 tab->ref.key_buff,
                                 tab->ref.key_length,HA_READ_KEY_EXACT);
  if (error &&
      error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
    error= report_error(table, error);
  else
  {
    error= 0;
    table->null_row= 0;
    ((Item_in_subselect *) item)->value= (!table->status &&
                                          (!cond || cond->val_int()) ? 1 :
                                          0);
  }

  DBUG_RETURN(error != 0);
}


subselect_uniquesubquery_engine::~subselect_uniquesubquery_engine()
{
  /* Tell handler we don't need the index anymore */
  tab->table->file->ha_index_end();
}


int subselect_indexsubquery_engine::exec()
{
  DBUG_ENTER("subselect_indexsubselect_engine::exec");
  int error;
  bool null_finding= 0;
  TABLE *table= tab->table;

  ((Item_in_subselect *) item)->value= 0;

  if (check_null)
  {
    /* We need to check for NULL if there wasn't a matching value */
    *tab->ref.null_ref_key= 0;			// Search first for not null
    ((Item_in_subselect *) item)->was_null= 0;
  }

  for (store_key **copy=tab->ref.key_copy ; *copy ; copy++)
  {
    if (tab->ref.key_err= (*copy)->copy())
    {
      table->status= STATUS_NOT_FOUND;
      DBUG_RETURN(1);
    }
  }

  if (!table->file->inited)
    table->file->ha_index_init(tab->ref.key);
  error= table->file->index_read(table->record[0],
                                 tab->ref.key_buff,
                                 tab->ref.key_length,HA_READ_KEY_EXACT);
  if (error &&
      error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
    error= report_error(table, error);
  else
  {
    for (;;)
    {
      error= 0;
      table->null_row= 0;
      if (!table->status)
      {
        if (!cond || cond->val_int())
        {
          if (null_finding)
            ((Item_in_subselect *) item)->was_null= 1;
          else
            ((Item_in_subselect *) item)->value= 1;
          break;
        }
        error= table->file->index_next_same(table->record[0],
                                            tab->ref.key_buff,
                                            tab->ref.key_length);
        if (error && error != HA_ERR_END_OF_FILE)
        {
          error= report_error(table, error);
          break;
        }
      }
      else
      {
        if (!check_null || null_finding)
          break;			/* We don't need to check nulls */
        *tab->ref.null_ref_key= 1;
        null_finding= 1;
        /* Check if there exists a row with a null value in the index */
        if ((error= (safe_index_read(tab) == 1)))
          break;
      }
    }
  }
  DBUG_RETURN(error != 0);
}


uint subselect_single_select_engine::cols()
{
  return select_lex->item_list.elements;
}


uint subselect_union_engine::cols()
{
  return unit->first_select()->item_list.elements;
}


uint8 subselect_single_select_engine::uncacheable()
{
  return select_lex->uncacheable;
}


uint8 subselect_union_engine::uncacheable()
{
  return unit->uncacheable;
}


void subselect_single_select_engine::exclude()
{
  select_lex->master_unit()->exclude_level();
}

void subselect_union_engine::exclude()
{
  unit->exclude_level();
}


void subselect_uniquesubquery_engine::exclude()
{
  //this never should be called
  DBUG_ASSERT(0);
}


table_map subselect_engine::calc_const_tables(TABLE_LIST *table)
{
  table_map map= 0;
  for(; table; table= table->next_leaf)
  {
    TABLE *tbl= table->table;
    if (tbl && tbl->const_table)
      map|= tbl->map;
  }
  return map;
}


table_map subselect_single_select_engine::upper_select_const_tables()
{
  return calc_const_tables((TABLE_LIST *) select_lex->outer_select()->
			   leaf_tables);
}


table_map subselect_union_engine::upper_select_const_tables()
{
  return calc_const_tables((TABLE_LIST *) unit->outer_select()->leaf_tables);
}


void subselect_single_select_engine::print(String *str)
{
  select_lex->print(thd, str);
}


void subselect_union_engine::print(String *str)
{
  unit->print(str);
}


void subselect_uniquesubquery_engine::print(String *str)
{
  str->append("<primary_index_lookup>(", 23);
  tab->ref.items[0]->print(str);
  str->append(" in ", 4);
  str->append(tab->table->real_name);
  KEY *key_info= tab->table->key_info+ tab->ref.key;
  str->append(" on ", 4);
  str->append(key_info->name);
  if (cond)
  {
    str->append(" where ", 7);
    cond->print(str);
  }
  str->append(')');
}


void subselect_indexsubquery_engine::print(String *str)
{
  str->append("<index_lookup>(", 15);
  tab->ref.items[0]->print(str);
  str->append(" in ", 4);
  str->append(tab->table->real_name);
  KEY *key_info= tab->table->key_info+ tab->ref.key;
  str->append(" on ", 4);
  str->append(key_info->name);
  if (check_null)
    str->append(" chicking NULL", 14);
    if (cond)
  {
    str->append(" where ", 7);
    cond->print(str);
  }
  str->append(')');
}

/*
  change select_result object of engine

  SINOPSYS
    subselect_single_select_engine::change_result()
    si		new subselect Item
    res		new select_result object

  RETURN
    FALSE OK
    TRUE  error
*/

bool subselect_single_select_engine::change_result(Item_subselect *si,
                                                 select_subselect *res)
{
  item= si;
  result= res;
  return select_lex->join->change_result(result);
}


/*
  change select_result object of engine

  SINOPSYS
    subselect_single_select_engine::change_result()
    si		new subselect Item
    res		new select_result object

  RETURN
    FALSE OK
    TRUE  error
*/

bool subselect_union_engine::change_result(Item_subselect *si,
                                         select_subselect *res)
{
  item= si;
  int rc= unit->change_result(res, result);
  result= res;
  return rc;
}


/*
  change select_result emulation, never should be called

  SINOPSYS
    subselect_single_select_engine::change_result()
    si		new subselect Item
    res		new select_result object

  RETURN
    FALSE OK
    TRUE  error
*/

bool subselect_uniquesubquery_engine::change_result(Item_subselect *si,
                                                  select_subselect *res)
{
  DBUG_ASSERT(0);
  return TRUE;
}


/*
  Report about presence of tables in subquery

  SINOPSYS
    subselect_single_select_engine::no_tables()

  RETURN
    TRUE  there are not tables used in subquery
    FALSE there are some tables in subquery
*/
bool subselect_single_select_engine::no_tables()
{
  return(select_lex->table_list.elements == 0);
}


/*
  Report about presence of tables in subquery

  SINOPSYS
    subselect_union_engine::no_tables()

  RETURN
    TRUE  there are not tables used in subquery
    FALSE there are some tables in subquery
*/
bool subselect_union_engine::no_tables()
{
  for (SELECT_LEX *sl= unit->first_select(); sl; sl= sl->next_select())
  {
    if (sl->table_list.elements)
      return FALSE;
  }
  return TRUE;
}


/*
  Report about presence of tables in subquery

  SINOPSYS
    subselect_uniquesubquery_engine::no_tables()

  RETURN
    TRUE  there are not tables used in subquery
    FALSE there are some tables in subquery
*/

bool subselect_uniquesubquery_engine::no_tables()
{
  /* returning value is correct, but this method should never be called */
  return 0;
}