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)
   - remove double 'having' & 'having_list' from JOIN
     (sql_select.h/sql_select.cc)

*/

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

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

Item_subselect::Item_subselect():
  Item_result_field(), engine_owner(1), value_assigned(0)
{
  assign_null();
  /*
    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(THD *thd, st_select_lex *select_lex,
		     select_subselect *result)
{

  DBUG_ENTER("Item_subselect::init");
  DBUG_PRINT("subs", ("select_lex 0x%xl", (long) select_lex));

  if (select_lex->next_select())
    engine= new subselect_union_engine(thd, select_lex->master_unit(), result,
				       this);
  else
    engine= new subselect_single_select_engine(thd, select_lex, result,
					       this);
  DBUG_VOID_RETURN;
}

Item_subselect::~Item_subselect()
{
  if (engine_owner)
    delete engine;
}

void Item_subselect::make_field (Send_field *tmp_field)
{
  if (null_value)
  {
    init_make_field(tmp_field,FIELD_TYPE_NULL);
    tmp_field->length=4;
  } else {
    init_make_field(tmp_field, ((result_type() == STRING_RESULT) ?
				FIELD_TYPE_VAR_STRING :
				(result_type() == INT_RESULT) ?
				FIELD_TYPE_LONGLONG : FIELD_TYPE_DOUBLE));
  }
}

bool Item_subselect::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
{
  int res= engine->prepare();
  if (!res)
  {
    // Is it one field subselect?
    if (engine->cols() > max_columns)
    {  
      my_message(ER_SUBSELECT_NO_1_COL, ER(ER_SUBSELECT_NO_1_COL), MYF(0));
      return 1;
    }
    fix_length_and_dec();
  }
  fixed= 1;
  return res;
}

bool Item_subselect::check_loop(uint id)
{
  DBUG_ENTER("Item_subselect::check_loop");
  if (Item_result_field::check_loop(id))
    DBUG_RETURN(1);
  
  DBUG_RETURN(engine->check_loop(id));
}

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

inline table_map Item_subselect::used_tables() const
{
  return (table_map) engine->depended() ? 1L : 0L; 
}

Item_singleval_subselect::Item_singleval_subselect(THD *thd,
						   st_select_lex *select_lex):
  Item_subselect()
{
  init(thd, select_lex, new select_singleval_subselect(this));
  max_columns= 1;
  maybe_null= 1;
}

void Item_singleval_subselect::fix_length_and_dec()
{
  engine->fix_length_and_dec();
  res_type= engine->type();
}

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

double Item_singleval_subselect::val () 
{
  if (engine->exec())
  {
    assign_null();
    return 0;
  }
  return real_value;
}

longlong Item_singleval_subselect::val_int () 
{
  if (engine->exec())
  {
    assign_null();
    return 0;
  }
  return int_value;
}

String *Item_singleval_subselect::val_str (String *str) 
{
  if (engine->exec() || null_value)
  {
    assign_null();
    return 0;
  }
  return &string_value;
}

Item_exists_subselect::Item_exists_subselect(THD *thd,
					     st_select_lex *select_lex):
  Item_subselect()
{
  init(thd, 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;
  select_lex->select_limit= 1; // we need only 1 row to determinate existence
}

void Item_exists_subselect::fix_length_and_dec()
{
  max_length= 1;
  
}

double Item_exists_subselect::val () 
{
  if (engine->exec())
  {
    assign_null();
    return 0;
  }
  return (double) value;
}

longlong Item_exists_subselect::val_int () 
{
  if (engine->exec())
  {
    assign_null();
    return 0;
  }
  return value;
}

String *Item_exists_subselect::val_str(String *str)
{
  if (engine->exec())
  {
    assign_null();
    return 0;
  }
  str->set(value,thd_charset());
  return str;
}


subselect_single_select_engine::subselect_single_select_engine(THD *thd, 
							       st_select_lex *select,
							       select_subselect *result,
							       Item_subselect *item):
  subselect_engine(thd, item, result),
    prepared(0), optimized(0), executed(0)
{
  select_lex= select;
  SELECT_LEX_UNIT *unit= select_lex->master_unit();
  unit->offset_limit_cnt= unit->global_parameters->offset_limit;
  unit->select_limit_cnt= unit->global_parameters->select_limit+
    unit->global_parameters ->offset_limit;
  if (unit->select_limit_cnt < unit->global_parameters->select_limit)
    unit->select_limit_cnt= HA_POS_ERROR;		// no limit
  if (unit->select_limit_cnt == HA_POS_ERROR)
    select_lex->options&= ~OPTION_FOUND_ROWS;
  join= new JOIN(thd, select_lex->item_list, select_lex->options, result);
  if (!join || !result)
  {
    //out of memory
    thd->fatal_error= 1;
    my_message(ER_OUT_OF_RESOURCES, ER(ER_OUT_OF_RESOURCES), MYF(0));
  } 
  unit->item= item;
  this->select_lex= select_lex;
}

subselect_union_engine::subselect_union_engine(THD *thd,
					       st_select_lex_unit *u,
					       select_subselect *result,
					       Item_subselect *item):
  subselect_engine(thd, item, result)
{
  unit= u;
  if( !result)
  {
    //out of memory
    thd->fatal_error= 1;
    my_message(ER_OUT_OF_RESOURCES, ER(ER_OUT_OF_RESOURCES), MYF(0));
  }
  unit->item= item;
}

int subselect_single_select_engine::prepare()
{
  if (prepared)
    return 0;
  prepared= 1;
  SELECT_LEX_NODE *save_select= thd->lex.current_select;
  thd->lex.current_select= select_lex;
  if(join->prepare((TABLE_LIST*) select_lex->table_list.first,
		   select_lex->where,
		   (ORDER*) select_lex->order_list.first,
		   (ORDER*) select_lex->group_list.first,
		   select_lex->having,
		   (ORDER*) 0, select_lex, 
		   select_lex->master_unit(), 0))
    return 1;
  thd->lex.current_select= save_select;
  return 0;
}

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

void subselect_single_select_engine::fix_length_and_dec()
{
  List_iterator_fast<Item> li(select_lex->item_list);
  Item *sel_item= li++;
  item->max_length= sel_item->max_length;
  res_type= sel_item->result_type();
  item->decimals= sel_item->decimals;
}

void subselect_union_engine::fix_length_and_dec()
{
  uint32 mlen= 0, len;
  Item *sel_item= 0;
  for(SELECT_LEX *sl= unit->first_select(); sl; sl= sl->next_select())
  {
    List_iterator_fast<Item> li(sl->item_list);
    Item *s_item= li++;
    if ((len= s_item->max_length))
      mlen= len;
    if (!sel_item)
      sel_item= s_item;
  }
  item->max_length= mlen;
  res_type= sel_item->result_type();
  item->decimals= sel_item->decimals;
}

int subselect_single_select_engine::exec()
{
  DBUG_ENTER("subselect_single_select_engine::exec");
  if (!optimized)
  {
    optimized=1;
    if (join->optimize())
    {
      executed= 1;
      DBUG_RETURN(join->error?join->error:1);
    }
  }
  if (select_lex->dependent && executed)
  {
    if (join->reinit())
      DBUG_RETURN(1);
    item->assign_null();
    item->assigned((executed= 0));
  }
  if (!executed)
  {
    SELECT_LEX_NODE *save_select= join->thd->lex.current_select;
    join->thd->lex.current_select= select_lex;
    join->exec();
    join->thd->lex.current_select= save_select;
    executed= 1;
    DBUG_RETURN(join->error||thd->fatal_error);
  }
  DBUG_RETURN(0);
}

int subselect_union_engine::exec()
{
  return unit->exec();
}

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

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

bool subselect_single_select_engine::depended()
{
  return select_lex->dependent;
}

bool subselect_union_engine::depended()
{
  return unit->dependent;
}

bool subselect_single_select_engine::check_loop(uint id)
{
  DBUG_ENTER("subselect_single_select_engine::check_loop");
  DBUG_RETURN(join->check_loop(id));
}

bool subselect_union_engine::check_loop(uint id)
{
  DBUG_ENTER("subselect_union_engine::check_loop");
  for (SELECT_LEX *sl= unit->first_select(); sl; sl= sl->next_select())
    if (sl->join && sl->join->check_loop(id))
      DBUG_RETURN(1);
  DBUG_RETURN(0);
}