mariadb/sql/sql_union.cc

/* Copyright (C) 2000-2003 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 */


/*
  UNION  of select's
  UNION's  were introduced by Monty and Sinisa <sinisa@mysql.com>
*/


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

int mysql_union(THD *thd, LEX *lex, select_result *result,
		SELECT_LEX_UNIT *unit)
{
  DBUG_ENTER("mysql_union");
  int res= 0;
  if (!(res= unit->prepare(thd, result)))
    res= unit->exec();
  res|= unit->cleanup();
  DBUG_RETURN(res);
}


/***************************************************************************
** store records in temporary table for UNION
***************************************************************************/

select_union::select_union(TABLE *table_par)
  :table(table_par), not_describe(0)
{
  bzero((char*) &info,sizeof(info));
  /*
    We can always use DUP_IGNORE because the temporary table will only
    contain a unique key if we are using not using UNION ALL
  */
  info.handle_duplicates= DUP_IGNORE;
}

select_union::~select_union()
{
}


int select_union::prepare(List<Item> &list, SELECT_LEX_UNIT *u)
{
  unit= u;
  return 0;
}


bool select_union::send_data(List<Item> &values)
{
  if (unit->offset_limit_cnt)
  {						// using limit offset,count
    unit->offset_limit_cnt--;
    return 0;
  }
  fill_record(table->field, values, 1);
  if (thd->net.report_error || write_record(table,&info))
  {
    if (thd->net.last_errno == ER_RECORD_FILE_FULL)
    {
      thd->clear_error(); // do not report user about table overflow
      if (create_myisam_from_heap(thd, table, &tmp_table_param,
				  info.last_errno, 1))
	return 1;
    }
    else
      return 1;
  }
  return 0;
}


bool select_union::send_eof()
{
  return 0;
}


bool select_union::flush()
{
  int error;
  if ((error=table->file->extra(HA_EXTRA_NO_CACHE)))
  {
    table->file->print_error(error,MYF(0));
    ::send_error(thd);
    return 1;
  }
  return 0;
}


int st_select_lex_unit::prepare(THD *thd, select_result *sel_result)
{
  SELECT_LEX *lex_select_save= thd->lex.current_select;
  SELECT_LEX *sl, *first_select;
  select_result *tmp_result;
  DBUG_ENTER("st_select_lex_unit::prepare");

  /*
    result object should be reassigned even if preparing already done for
    max/min subquery (ALL/ANY optimization)
  */
  result= sel_result;

  if (prepared)
    DBUG_RETURN(0);
  prepared= 1;
  res= 0;
  TMP_TABLE_PARAM tmp_table_param;
  
  bzero((char *)&tmp_table_param,sizeof(TMP_TABLE_PARAM));
  thd->lex.current_select= sl= first_select= first_select_in_union();
  found_rows_for_union= first_select->options & OPTION_FOUND_ROWS;

  /* Global option */

  if (first_select->next_select())
  {
    if (!(tmp_result= union_result= new select_union(0)))
      goto err;
    union_result->not_describe= 1;
    union_result->tmp_table_param= tmp_table_param;
  }
  else
  {
    tmp_result= sel_result;
    // single select should be processed like select in p[arantses
    first_select->braces= 1;
  }

  for (;sl; sl= sl->next_select())
  {
    JOIN *join= new JOIN(thd, sl->item_list, 
			 sl->options | thd->options | SELECT_NO_UNLOCK,
			 tmp_result);
    thd->lex.current_select= sl;
    offset_limit_cnt= sl->offset_limit;
    select_limit_cnt= sl->select_limit+sl->offset_limit;
    if (select_limit_cnt < sl->select_limit)
      select_limit_cnt= HA_POS_ERROR;		// no limit
    if (select_limit_cnt == HA_POS_ERROR || sl->braces)
      sl->options&= ~OPTION_FOUND_ROWS;
    
    res= join->prepare(&sl->ref_pointer_array,
		       (TABLE_LIST*) sl->table_list.first, sl->with_wild,
		       sl->where,
		       ((sl->braces) ? sl->order_list.elements : 0) +
		       sl->group_list.elements,
		       (sl->braces) ? 
		       (ORDER *)sl->order_list.first : (ORDER *) 0,
		       (ORDER*) sl->group_list.first,
		       sl->having,
		       (ORDER*) NULL,
		       sl, this);
    if (res || thd->is_fatal_error)
      goto err;
    if (sl == first_select)
    {
      types.empty();
      List_iterator_fast<Item> it(sl->item_list);
      Item *item;
      while((item= it++))
      {
	types.push_back(new Item_type_holder(thd, item));
      }

      if (thd->is_fatal_error)
	goto err; // out of memory
    }
    else
    {
      if (types.elements != sl->item_list.elements)
      {
	my_message(ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT,
		   ER(ER_WRONG_NUMBER_OF_COLUMNS_IN_SELECT),MYF(0));
	goto err;
      }
      List_iterator_fast<Item> it(sl->item_list);
      List_iterator_fast<Item> tp(types);	
      Item *type, *item;
      while((type= tp++, item= it++))
      {
	((Item_type_holder*)type)->join_types(thd, item);
      }
    }
  }

  if (first_select->next_select())
  {
    tmp_table_param.field_count= types.elements;
    if (!(table= create_tmp_table(thd, &tmp_table_param, types,
				  (ORDER*) 0, !union_option, 1, 
				  (first_select_in_union()->options |
				   thd->options |
				   TMP_TABLE_ALL_COLUMNS),
				  HA_POS_ERROR, (char*) "")))
      goto err;
    table->file->extra(HA_EXTRA_WRITE_CACHE);
    table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);
    bzero((char*) &result_table_list, sizeof(result_table_list));
    result_table_list.db= (char*) "";
    result_table_list.real_name= result_table_list.alias= (char*) "union";
    result_table_list.table= table;
    union_result->set_table(table);

    item_list.empty();
    thd->lex.current_select= lex_select_save;
    {
      Field **field;
      for (field= table->field; *field; field++)
      {
	if (item_list.push_back(new Item_field(*field)))
	  DBUG_RETURN(-1);
      }
    }
  }
  else
    first_select->braces= 0; // remove our changes

  thd->lex.current_select= lex_select_save;

  DBUG_RETURN(res || thd->is_fatal_error ? 1 : 0);

err:
  thd->lex.current_select= lex_select_save;
  DBUG_RETURN(-1);
}


int st_select_lex_unit::exec()
{
  SELECT_LEX *lex_select_save= thd->lex.current_select;
  SELECT_LEX *select_cursor=first_select_in_union();
  ulonglong add_rows=0;
  DBUG_ENTER("st_select_lex_unit::exec");

  if (executed && !uncacheable)
    DBUG_RETURN(0);
  executed= 1;
  
  if (uncacheable || !item || !item->assigned())
  {
    if (optimized && item && item->assigned())
    {
      item->assigned(0); // We will reinit & rexecute unit
      item->reset();
      table->file->delete_all_rows();
    }
    for (SELECT_LEX *sl= select_cursor; sl; sl= sl->next_select())
    {
      ha_rows records_at_start= 0;
      thd->lex.current_select= sl;

      if (optimized)
	res= sl->join->reinit();
      else
      {
	if (sl != global_parameters)
	{
	  offset_limit_cnt= sl->offset_limit;
	  select_limit_cnt= sl->select_limit+sl->offset_limit;
	}
	else
	{
	  offset_limit_cnt= 0;
	  /*
	    We can't use LIMIT at this stage if we are using ORDER BY for the
	    whole query
	  */
	  if (sl->order_list.first)
	    select_limit_cnt= HA_POS_ERROR;
	  else
	    select_limit_cnt= sl->select_limit+sl->offset_limit;
	}
	if (select_limit_cnt < sl->select_limit)
	  select_limit_cnt= HA_POS_ERROR;		// no limit

	/*
	  When using braces, SQL_CALC_FOUND_ROWS affects the whole query.
	  We don't calculate found_rows() per union part
	*/
	if (select_limit_cnt == HA_POS_ERROR || sl->braces)
	  sl->options&= ~OPTION_FOUND_ROWS;
	else 
	{
	  /*
	    We are doing an union without braces.  In this case
	    SQL_CALC_FOUND_ROWS should be done on all sub parts
	  */
	  sl->options|= found_rows_for_union;
	}
	sl->join->select_options=sl->options;
	/*
	  As far as union share table space we should reassign table map,
	  which can be spoiled by 'prepare' of JOIN of other UNION parts
	  if it use same tables
	*/
	uint tablenr=0;
	for (TABLE_LIST *table_list= (TABLE_LIST*) sl->table_list.first;
	     table_list;
	     table_list= table_list->next, tablenr++)
	{
	  if (table_list->shared)
	  {
	    /*
	      review notes: Check it carefully. I still can't understand
	      why I should not touch table->used_keys. For my point of
	      view we should do here same procedura as it was done by
	      setup_table
	    */
	    setup_table_map(table_list->table, table_list, tablenr);
	  }
	}
	res= sl->join->optimize();
      }
      if (!res)
      {
	records_at_start= table->file->records;
	sl->join->exec();
	res= sl->join->error;
	offset_limit_cnt= sl->offset_limit;
	if (!res && union_result->flush())
	{
	  thd->lex.current_select= lex_select_save;
	  DBUG_RETURN(1);
	}
      }
      if (res)
      {
	thd->lex.current_select= lex_select_save;
	DBUG_RETURN(res);
      }
      /* Needed for the following test and for records_at_start in next loop */
      table->file->info(HA_STATUS_VARIABLE);
      if (found_rows_for_union & sl->options)
      {
	/*
	  This is a union without braces. Remember the number of rows that
	  could also have been part of the result set.
	  We get this from the difference of between total number of possible
	  rows and actual rows added to the temporary table.
	*/
	add_rows+= (ulonglong) (thd->limit_found_rows - (ulonglong)
			      ((table->file->records -  records_at_start)));
      }
    }
  }
  optimized= 1;

  /* Send result to 'result' */


  res= -1;
  {
    List<Item_func_match> empty_list;
    empty_list.empty();

    if (!thd->is_fatal_error)				// Check if EOM
    {
      ulong options= thd->options;
      thd->lex.current_select= fake_select_lex;
      offset_limit_cnt= global_parameters->offset_limit;
      select_limit_cnt= global_parameters->select_limit +
	global_parameters->offset_limit;

      if (select_limit_cnt < global_parameters->select_limit)
	select_limit_cnt= HA_POS_ERROR;		// no limit
      if (select_limit_cnt == HA_POS_ERROR)
	options&= ~OPTION_FOUND_ROWS;
      else if (found_rows_for_union && !thd->lex.describe)
	options|= OPTION_FOUND_ROWS;
      fake_select_lex->ftfunc_list= &empty_list;
      fake_select_lex->table_list.link_in_list((byte *)&result_table_list,
					       (byte **)
					       &result_table_list.next);
      JOIN *join= fake_select_lex->join;
      if (!join)
      {
	/*
	  allocate JOIN for fake select only once (privent
	  mysql_select automatic allocation)
	*/
	fake_select_lex->join= new JOIN(thd, item_list, thd->options, result);
	/*
	  Fake st_select_lex should have item list for correctref_array
	  allocation.
	*/
	fake_select_lex->item_list= item_list;
      }
      else
      {
	JOIN_TAB *tab,*end;
	for (tab=join->join_tab,end=tab+join->tables ; tab != end ; tab++)
	{
	  delete tab->select;
	  delete tab->quick;
	}
	join->init(thd, item_list, thd->options, result);
      }
      res= mysql_select(thd, &fake_select_lex->ref_pointer_array,
			&result_table_list,
			0, item_list, NULL,
			global_parameters->order_list.elements,
			(ORDER*)global_parameters->order_list.first,
			(ORDER*) NULL, NULL, (ORDER*) NULL,
			options | SELECT_NO_UNLOCK,
			result, this, fake_select_lex);
      if (!res)
	thd->limit_found_rows = (ulonglong)table->file->records + add_rows;
      /*
	Mark for slow query log if any of the union parts didn't use
	indexes efficiently
      */
    }
  }
  thd->lex.current_select= lex_select_save;
  DBUG_RETURN(res);
}


int st_select_lex_unit::cleanup()
{
  int error= 0;
  DBUG_ENTER("st_select_lex_unit::cleanup");

  if (union_result)
  {
    delete union_result;
    if (table)
      free_tmp_table(thd, table);
    table= 0; // Safety
  }
  JOIN *join;
  for (SELECT_LEX *sl= first_select_in_union(); sl; sl= sl->next_select())
  {
    if ((join= sl->join))
    {
      error|= sl->join->cleanup();
      delete join;
    }
  }
  if (fake_select_lex && (join= fake_select_lex->join))
  {
    join->tables_list= 0;
    join->tables= 0;
    error|= join->cleanup();
    delete join;
  }
  DBUG_RETURN(error);
}