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/* Copyright (C) 2002-2003 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 */
/*
Derived tables
These were introduced by Sinisa <sinisa@mysql.com>
*/
#include "config.h"
#include "drizzled/sql_select.h"
/*
Call given derived table processor (preparing or filling tables)
SYNOPSIS
mysql_handle_derived()
lex LEX for this thread
processor procedure of derived table processing
RETURN
false OK
true Error
*/
bool mysql_handle_derived(LEX *lex, bool (*processor)(Session*, LEX*, TableList*))
{
bool res= false;
if (lex->derived_tables)
{
lex->session->derived_tables_processing= true;
for (Select_Lex *sl= lex->all_selects_list; sl; sl= sl->next_select_in_list())
{
for (TableList *cursor= sl->get_table_list(); cursor; cursor= cursor->next_local)
{
if ((res= (*processor)(lex->session, lex, cursor)))
goto out;
}
if (lex->describe)
{
/*
Force join->join_tmp creation, because we will use this JOIN
twice for EXPLAIN and we have to have unchanged join for EXPLAINing
*/
sl->uncacheable|= UNCACHEABLE_EXPLAIN;
sl->master_unit()->uncacheable|= UNCACHEABLE_EXPLAIN;
}
}
}
out:
lex->session->derived_tables_processing= false;
return res;
}
/*
Create temporary table structure (but do not fill it)
SYNOPSIS
mysql_derived_prepare()
session Thread handle
lex LEX for this thread
orig_table_list TableList for the upper SELECT
IMPLEMENTATION
Derived table is resolved with temporary table.
After table creation, the above TableList is updated with a new table.
This function is called before any command containing derived table
is executed.
Derived tables is stored in session->derived_tables and freed in
close_thread_tables()
RETURN
false OK
true Error
*/
bool mysql_derived_prepare(Session *session, LEX *, TableList *orig_table_list)
{
Select_Lex_Unit *unit= orig_table_list->derived;
uint64_t create_options;
bool res= false;
if (unit)
{
Select_Lex *first_select= unit->first_select();
Table *table= 0;
select_union *derived_result;
/* prevent name resolving out of derived table */
for (Select_Lex *sl= first_select; sl; sl= sl->next_select())
sl->context.outer_context= 0;
if (!(derived_result= new select_union))
return(true); // out of memory
// Select_Lex_Unit::prepare correctly work for single select
if ((res= unit->prepare(session, derived_result, 0)))
goto exit;
create_options= (first_select->options | session->options | TMP_TABLE_ALL_COLUMNS);
/*
Temp table is created so that it hounours if UNION without ALL is to be
processed
As 'distinct' parameter we always pass false (0), because underlying
query will control distinct condition by itself. Correct test of
distinct underlying query will be is_union &&
!unit->union_distinct->next_select() (i.e. it is union and last distinct
SELECT is last SELECT of UNION).
*/
if ((res= derived_result->create_result_table(session, &unit->types, false,
create_options,
orig_table_list->alias,
false)))
goto exit;
table= derived_result->table;
exit:
/*
if it is preparation PS only or commands that need only VIEW structure
then we do not need real data and we can skip execution (and parameters
is not defined, too)
*/
if (res)
{
if (table)
table->free_tmp_table(session);
delete derived_result;
}
else
{
if (! session->fill_derived_tables())
{
delete derived_result;
derived_result= NULL;
}
orig_table_list->derived_result= derived_result;
orig_table_list->table= table;
orig_table_list->table_name= table->s->table_name.str;
orig_table_list->table_name_length= table->s->table_name.length;
table->derived_select_number= first_select->select_number;
table->s->tmp_table= TEMP_TABLE;
orig_table_list->db= (char *)"";
orig_table_list->db_length= 0;
/* Force read of table stats in the optimizer */
table->cursor->info(HA_STATUS_VARIABLE);
/* Add new temporary table to list of open derived tables */
table->next= session->derived_tables;
session->derived_tables= table;
}
}
return(res);
}
/*
fill derived table
SYNOPSIS
mysql_derived_filling()
session Thread handle
lex LEX for this thread
unit node that contains all SELECT's for derived tables
orig_table_list TableList for the upper SELECT
IMPLEMENTATION
Derived table is resolved with temporary table. It is created based on the
queries defined. After temporary table is filled, if this is not EXPLAIN,
then the entire unit / node is deleted. unit is deleted if UNION is used
for derived table and node is deleted is it is a simple SELECT.
If you use this function, make sure it's not called at prepare.
Due to evaluation of LIMIT clause it can not be used at prepared stage.
RETURN
false OK
true Error
*/
bool mysql_derived_filling(Session *session, LEX *lex, TableList *orig_table_list)
{
Table *table= orig_table_list->table;
Select_Lex_Unit *unit= orig_table_list->derived;
bool res= false;
/*check that table creation pass without problem and it is derived table */
if (table && unit)
{
Select_Lex *first_select= unit->first_select();
select_union *derived_result= orig_table_list->derived_result;
Select_Lex *save_current_select= lex->current_select;
if (unit->is_union())
{
/* execute union without clean up */
res= unit->exec();
}
else
{
unit->set_limit(first_select);
if (unit->select_limit_cnt == HA_POS_ERROR)
first_select->options&= ~OPTION_FOUND_ROWS;
lex->current_select= first_select;
res= mysql_select(session, &first_select->ref_pointer_array,
(TableList*) first_select->table_list.first,
first_select->with_wild,
first_select->item_list, first_select->where,
(first_select->order_list.elements+
first_select->group_list.elements),
(order_st *) first_select->order_list.first,
(order_st *) first_select->group_list.first,
first_select->having,
(first_select->options | session->options | SELECT_NO_UNLOCK),
derived_result, unit, first_select);
}
if (! res)
{
/*
Here we entirely fix both TableList and list of SELECT's as
there were no derived tables
*/
if (derived_result->flush())
res= true;
if (! lex->describe)
unit->cleanup();
}
else
unit->cleanup();
lex->current_select= save_current_select;
}
return res;
}
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