~drizzle-trunk/drizzle/development

/* 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; version 2 of the License.

   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 <drizzled/server_includes.h>

#include <drizzled/sql_select.h>

#include <drizzled/error.h>

#include <drizzled/item/type_holder.h>

#include <drizzled/sql_base.h>

bool mysql_union(Session *session, LEX *, select_result *result,

                 SELECT_LEX_UNIT *unit, ulong setup_tables_done_option)

{

  bool res;

  if (!(res= unit->prepare(session, result, SELECT_NO_UNLOCK |

                           setup_tables_done_option)))

    res= unit->exec();

  if (res)

    res|= unit->cleanup();

  return(res);

}

/***************************************************************************

** store records in temporary table for UNION

***************************************************************************/

int select_union::prepare(List<Item> &, SELECT_LEX_UNIT *u)

{

  unit= u;

  return 0;

}

bool select_union::send_data(List<Item> &values)

{

  int error= 0;

  if (unit->offset_limit_cnt)

  {						// using limit offset,count

    unit->offset_limit_cnt--;

    return 0;

  }

  fill_record(session, table->field, values, 1);

  if (session->is_error())

    return 1;

  if ((error= table->file->ha_write_row(table->record[0])))

  {

    /* create_myisam_from_heap will generate error if needed */

    if (table->file->is_fatal_error(error, HA_CHECK_DUP) &&

        create_myisam_from_heap(session, table, tmp_table_param.start_recinfo,

                                &tmp_table_param.recinfo, error, 1))

      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));

    return 1;

  }

  return 0;

}

/*

  Create a temporary table to store the result of select_union.

  SYNOPSIS

    select_union::create_result_table()

      session                thread handle

      column_types       a list of items used to define columns of the

                         temporary table

      is_union_distinct  if set, the temporary table will eliminate

                         duplicates on insert

      options            create options

      table_alias        name of the temporary table

      bit_fields_as_long convert bit fields to uint64_t

  DESCRIPTION

    Create a temporary table that is used to store the result of a UNION,

    derived table, or a materialized cursor.

  RETURN VALUE

    0                    The table has been created successfully.

    1                    create_tmp_table failed.

*/

bool

select_union::create_result_table(Session *session_arg, List<Item> *column_types,

                                  bool is_union_distinct, uint64_t options,

                                  const char *table_alias,

                                  bool bit_fields_as_long)

{

  assert(table == 0);

  tmp_table_param.init();

  tmp_table_param.field_count= column_types->elements;

  tmp_table_param.bit_fields_as_long= bit_fields_as_long;

  if (! (table= create_tmp_table(session_arg, &tmp_table_param, *column_types,

                                 (order_st*) 0, is_union_distinct, 1,

                                 options, HA_POS_ERROR, (char*) table_alias)))

    return true;

  table->file->extra(HA_EXTRA_WRITE_CACHE);

  table->file->extra(HA_EXTRA_IGNORE_DUP_KEY);

  return false;

}

/**

  Reset and empty the temporary table that stores the materialized query result.

  @note The cleanup performed here is exactly the same as for the two temp

  tables of JOIN - exec_tmp_table_[1 | 2].

*/

void select_union::cleanup()

{

  table->file->extra(HA_EXTRA_RESET_STATE);

  table->file->ha_delete_all_rows();

  free_io_cache(table);

  filesort_free_buffers(table,0);

}

/*

  initialization procedures before fake_select_lex preparation()

  SYNOPSIS

    st_select_lex_unit::init_prepare_fake_select_lex()

    session		- thread handler

  RETURN

    options of SELECT

*/

void

st_select_lex_unit::init_prepare_fake_select_lex(Session *session_arg)

{

  session_arg->lex->current_select= fake_select_lex;

  fake_select_lex->table_list.link_in_list((unsigned char *)&result_table_list,

					   (unsigned char **)

					   &result_table_list.next_local);

  fake_select_lex->context.table_list=

    fake_select_lex->context.first_name_resolution_table=

    fake_select_lex->get_table_list();

  for (order_st *order= (order_st *) global_parameters->order_list.first;

       order;

       order= order->next)

    order->item= &order->item_ptr;

  for (order_st *order= (order_st *)global_parameters->order_list.first;

       order;

       order=order->next)

  {

    (*order->item)->walk(&Item::change_context_processor, 0,

                         (unsigned char*) &fake_select_lex->context);

  }

}

bool st_select_lex_unit::prepare(Session *session_arg, select_result *sel_result,

                                 uint32_t additional_options)

{

  SELECT_LEX *lex_select_save= session_arg->lex->current_select;

  SELECT_LEX *sl, *first_sl= first_select();

  select_result *tmp_result;

  bool is_union_select;

  Table *empty_table= 0;

  describe= test(additional_options & SELECT_DESCRIBE);

  /*

    result object should be reassigned even if preparing already done for

    max/min subquery (ALL/ANY optimization)

  */

  result= sel_result;

  if (prepared)

  {

    if (describe)

    {

      /* fast reinit for EXPLAIN */

      for (sl= first_sl; sl; sl= sl->next_select())

      {

	sl->join->result= result;

	select_limit_cnt= HA_POS_ERROR;

	offset_limit_cnt= 0;

	if (result->prepare(sl->join->fields_list, this))

	{

	  return(true);

	}

	sl->join->select_options|= SELECT_DESCRIBE;

	sl->join->reinit();

      }

    }

    return(false);

  }

  prepared= 1;

  saved_error= false;

  session_arg->lex->current_select= sl= first_sl;

  found_rows_for_union= first_sl->options & OPTION_FOUND_ROWS;

  is_union_select= is_union() || fake_select_lex;

  /* Global option */

  if (is_union_select)

  {

    if (!(tmp_result= union_result= new select_union))

      goto err;

    if (describe)

      tmp_result= sel_result;

  }

  else

    tmp_result= sel_result;

  sl->context.resolve_in_select_list= true;

  for (;sl; sl= sl->next_select())

  {

    bool can_skip_order_by;

    sl->options|=  SELECT_NO_UNLOCK;

    JOIN *join= new JOIN(session_arg, sl->item_list,

			 sl->options | session_arg->options | additional_options,

			 tmp_result);

    /*

      setup_tables_done_option should be set only for very first SELECT,

      because it protect from secont setup_tables call for select-like non

      select commands (DELETE/INSERT/...) and they use only very first

      SELECT (for union it can be only INSERT ... SELECT).

    */

    additional_options&= ~OPTION_SETUP_TABLES_DONE;

    if (!join)

      goto err;

    session_arg->lex->current_select= sl;

    can_skip_order_by= is_union_select && !(sl->braces && sl->explicit_limit);

    saved_error= join->prepare(&sl->ref_pointer_array,

                               (TableList*) sl->table_list.first,

                               sl->with_wild,

                               sl->where,

                               (can_skip_order_by ? 0 :

                                sl->order_list.elements) +

                               sl->group_list.elements,

                               can_skip_order_by ?

                               (order_st*) 0 : (order_st *)sl->order_list.first,

                               (order_st*) sl->group_list.first,

                               sl->having,

                               (is_union_select ? (order_st*) 0 :

                                (order_st*) session_arg->lex->proc_list.first),

                               sl, this);

    /* There are no * in the statement anymore (for PS) */

    sl->with_wild= 0;

    if (saved_error || (saved_error= session_arg->is_fatal_error))

      goto err;

    /*

      Use items list of underlaid select for derived tables to preserve

      information about fields lengths and exact types

    */

    if (!is_union_select)

      types= first_sl->item_list;

    else if (sl == first_sl)

    {

      /*

        We need to create an empty table object. It is used

        to create tmp_table fields in Item_type_holder.

        The main reason of this is that we can't create

        field object without table.

      */

      assert(!empty_table);

      empty_table= (Table*) session->calloc(sizeof(Table));

      types.empty();

      List_iterator_fast<Item> it(sl->item_list);

      Item *item_tmp;

      while ((item_tmp= it++))

      {

	/* Error's in 'new' will be detected after loop */

	types.push_back(new Item_type_holder(session_arg, item_tmp));

      }

      if (session_arg->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_tmp;

      while ((type= tp++, item_tmp= it++))

      {

        if (((Item_type_holder*)type)->join_types(session_arg, item_tmp))

	  return(true);

      }

    }

  }

  if (is_union_select)

  {

    /*

      Check that it was possible to aggregate

      all collations together for UNION.

    */

    List_iterator_fast<Item> tp(types);

    Item *type;

    uint64_t create_options;

    while ((type= tp++))

    {

      if (type->result_type() == STRING_RESULT &&

          type->collation.derivation == DERIVATION_NONE)

      {

        my_error(ER_CANT_AGGREGATE_NCOLLATIONS, MYF(0), "UNION");

        goto err;

      }

    }

    create_options= (first_sl->options | session_arg->options |

                     TMP_TABLE_ALL_COLUMNS);

    if (union_result->create_result_table(session, &types, test(union_distinct),

                                          create_options, "", false))

      goto err;

    memset(&result_table_list, 0, sizeof(result_table_list));

    result_table_list.db= (char*) "";

    result_table_list.table_name= result_table_list.alias= (char*) "union";

    result_table_list.table= table= union_result->table;

    session_arg->lex->current_select= lex_select_save;

    if (!item_list.elements)

    {

      saved_error= table->fill_item_list(&item_list);

      if (saved_error)

        goto err;

    }

    else

    {

      /*

        We're in execution of a prepared statement or stored procedure:

        reset field items to point at fields from the created temporary table.

      */

      assert(1);

    }

  }

  session_arg->lex->current_select= lex_select_save;

  return(saved_error || session_arg->is_fatal_error);

err:

  session_arg->lex->current_select= lex_select_save;

  return(true);

}

bool st_select_lex_unit::exec()

{

  SELECT_LEX *lex_select_save= session->lex->current_select;

  SELECT_LEX *select_cursor=first_select();

  uint64_t add_rows=0;

  ha_rows examined_rows= 0;

  if (executed && !uncacheable && !describe)

    return(false);

  executed= 1;

  if (uncacheable || !item || !item->assigned() || describe)

  {

    if (item)

      item->reset_value_registration();

    if (optimized && item)

    {

      if (item->assigned())

      {

        item->assigned(0); // We will reinit & rexecute unit

        item->reset();

        table->file->ha_delete_all_rows();

      }

      /* re-enabling indexes for next subselect iteration */

      if (union_distinct && table->file->ha_enable_indexes(HA_KEY_SWITCH_ALL))

      {

        assert(0);

      }

    }

    for (SELECT_LEX *sl= select_cursor; sl; sl= sl->next_select())

    {

      ha_rows records_at_start= 0;

      session->lex->current_select= sl;

      if (optimized)

	saved_error= sl->join->reinit();

      else

      {

        set_limit(sl);

	if (sl == global_parameters || describe)

	{

	  offset_limit_cnt= 0;

	  /*

	    We can't use LIMIT at this stage if we are using order_st BY for the

	    whole query

	  */

	  if (sl->order_list.first || describe)

	    select_limit_cnt= HA_POS_ERROR;

        }

        /*

          When using braces, SQL_CALC_FOUND_ROWS affects the whole query:

          we don't calculate found_rows() per union part.

          Otherwise, SQL_CALC_FOUND_ROWS should be done on all sub parts.

        */

        sl->join->select_options=

          (select_limit_cnt == HA_POS_ERROR || sl->braces) ?

          sl->options & ~OPTION_FOUND_ROWS : sl->options | found_rows_for_union;

        if (sl->join->flatten_subqueries())

          return(true);

	saved_error= sl->join->optimize();

      }

      if (!saved_error)

      {

	records_at_start= table->file->stats.records;

	sl->join->exec();

        if (sl == union_distinct)

	{

	  if (table->file->ha_disable_indexes(HA_KEY_SWITCH_ALL))

	    return(true);

	  table->no_keyread=1;

	}

	saved_error= sl->join->error;

	offset_limit_cnt= (ha_rows)(sl->offset_limit ?

                                    sl->offset_limit->val_uint() :

                                    0);

	if (!saved_error)

	{

	  examined_rows+= session->examined_row_count;

	  if (union_result->flush())

	  {

	    session->lex->current_select= lex_select_save;

	    return(1);

	  }

	}

      }

      if (saved_error)

      {

	session->lex->current_select= lex_select_save;

	return(saved_error);

      }

      /* Needed for the following test and for records_at_start in next loop */

      int error= table->file->info(HA_STATUS_VARIABLE);

      if(error)

      {

        table->file->print_error(error, MYF(0));

        return(1);

      }

      if (found_rows_for_union && !sl->braces &&

          select_limit_cnt != HA_POS_ERROR)

      {

	/*

	  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+= (uint64_t) (session->limit_found_rows - (uint64_t)

			      ((table->file->stats.records -  records_at_start)));

      }

    }

  }

  optimized= 1;

  /* Send result to 'result' */

  saved_error= true;

  {

    if (!session->is_fatal_error)				// Check if EOM

    {

      set_limit(global_parameters);

      init_prepare_fake_select_lex(session);

      JOIN *join= fake_select_lex->join;

      if (!join)

      {

	/*

	  allocate JOIN for fake select only once (prevent

	  mysql_select automatic allocation)

          TODO: The above is nonsense. mysql_select() will not allocate the

          join if one already exists. There must be some other reason why we

          don't let it allocate the join. Perhaps this is because we need

          some special parameter values passed to join constructor?

	*/

	if (!(fake_select_lex->join= new JOIN(session, item_list,

					      fake_select_lex->options, result)))

	{

	  fake_select_lex->table_list.empty();

	  return(true);

	}

        fake_select_lex->join->no_const_tables= true;

	/*

	  Fake st_select_lex should have item list for correctref_array

	  allocation.

	*/

	fake_select_lex->item_list= item_list;

        saved_error= mysql_select(session, &fake_select_lex->ref_pointer_array,

                              &result_table_list,

                              0, item_list, NULL,

                              global_parameters->order_list.elements,

                              (order_st*)global_parameters->order_list.first,

                              (order_st*) NULL, NULL, (order_st*) NULL,

                              fake_select_lex->options | SELECT_NO_UNLOCK,

                              result, this, fake_select_lex);

      }

      else

      {

        if (describe)

        {

          /*

            In EXPLAIN command, constant subqueries that do not use any

            tables are executed two times:

             - 1st time is a real evaluation to get the subquery value

             - 2nd time is to produce EXPLAIN output rows.

            1st execution sets certain members (e.g. select_result) to perform

            subquery execution rather than EXPLAIN line production. In order

            to reset them back, we re-do all of the actions (yes it is ugly):

          */

	  join->init(session, item_list, fake_select_lex->options, result);

          saved_error= mysql_select(session, &fake_select_lex->ref_pointer_array,

                                &result_table_list,

                                0, item_list, NULL,

                                global_parameters->order_list.elements,

                                (order_st*)global_parameters->order_list.first,

                                (order_st*) NULL, NULL, (order_st*) NULL,

                                fake_select_lex->options | SELECT_NO_UNLOCK,

                                result, this, fake_select_lex);

        }

        else

        {

          join->examined_rows= 0;

          saved_error= join->reinit();

          join->exec();

        }

      }

      fake_select_lex->table_list.empty();

      if (!saved_error)

      {

	session->limit_found_rows = (uint64_t)table->file->stats.records + add_rows;

        session->examined_row_count+= examined_rows;

      }

      /*

	Mark for slow query log if any of the union parts didn't use

	indexes efficiently

      */

    }

  }

  session->lex->current_select= lex_select_save;

  return(saved_error);

}

bool st_select_lex_unit::cleanup()

{

  int error= 0;

  if (cleaned)

  {

    return(false);

  }

  cleaned= 1;

  if (union_result)

  {

    delete union_result;

    union_result=0; // Safety

    if (table)

      table->free_tmp_table(session);

    table= 0; // Safety

  }

  for (SELECT_LEX *sl= first_select(); sl; sl= sl->next_select())

    error|= sl->cleanup();

  if (fake_select_lex)

  {

    JOIN *join;

    if ((join= fake_select_lex->join))

    {

      join->tables_list= 0;

      join->tables= 0;

    }

    error|= fake_select_lex->cleanup();

    if (fake_select_lex->order_list.elements)

    {

      order_st *ord;

      for (ord= (order_st*)fake_select_lex->order_list.first; ord; ord= ord->next)

        (*ord->item)->cleanup();

    }

  }

  return(error);

}

void st_select_lex_unit::reinit_exec_mechanism()

{

  prepared= optimized= executed= 0;

}

/*

  change select_result object of unit

  SYNOPSIS

    st_select_lex_unit::change_result()

    result	new select_result object

    old_result	old select_result object

  RETURN

    false - OK

    true  - error

*/

bool st_select_lex_unit::change_result(select_result_interceptor *new_result,

                                       select_result_interceptor *old_result)

{

  bool res= false;

  for (SELECT_LEX *sl= first_select(); sl; sl= sl->next_select())

  {

    if (sl->join && sl->join->result == old_result)

      if (sl->join->change_result(new_result))

	return true;

  }

  if (fake_select_lex && fake_select_lex->join)

    res= fake_select_lex->join->change_result(new_result);

  return (res);

}

/*

  Get column type information for this unit.

  SYNOPSIS

    st_select_lex_unit::get_unit_column_types()

  DESCRIPTION

    For a single-select the column types are taken

    from the list of selected items. For a union this function

    assumes that st_select_lex_unit::prepare has been called

    and returns the type holders that were created for unioned

    column types of all selects.

  NOTES

    The implementation of this function should be in sync with

    st_select_lex_unit::prepare()

*/

List<Item> *st_select_lex_unit::get_unit_column_types()

{

  SELECT_LEX *sl= first_select();

  if (is_union())

  {

    assert(prepared);

    /* Types are generated during prepare */

    return &types;

  }

  return &sl->item_list;

}

bool st_select_lex::cleanup()

{

  bool error= false;

  if (join)

  {

    assert((st_select_lex*)join->select_lex == this);

    error= join->destroy();

    delete join;

    join= 0;

  }

  for (SELECT_LEX_UNIT *lex_unit= first_inner_unit(); lex_unit ;

       lex_unit= lex_unit->next_unit())

  {

    error= (bool) ((uint) error | (uint) lex_unit->cleanup());

  }

  non_agg_fields.empty();

  inner_refs_list.empty();

  return(error);