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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; 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 */
/*
Derived tables
These were introduced by Sinisa <sinisa@mysql.com>
*/
#include "mysql_priv.h"
#include "sql_select.h"
#include "sql_acl.h"
static int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *s,
TABLE_LIST *t);
/*
Resolve derived tables in all queries
SYNOPSIS
mysql_handle_derived()
lex LEX for this thread
RETURN
0 ok
-1 Error
1 Error and error message given
*/
int
mysql_handle_derived(LEX *lex)
{
if (lex->derived_tables)
{
for (SELECT_LEX *sl= lex->all_selects_list;
sl;
sl= sl->next_select_in_list())
{
for (TABLE_LIST *cursor= sl->get_table_list();
cursor;
cursor= cursor->next)
{
int res;
if (cursor->derived && (res=mysql_derived(lex->thd, lex,
cursor->derived,
cursor)))
{
return res;
}
}
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;
}
}
}
return 0;
}
/*
Resolve derived tables in all queries
SYNOPSIS
mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit, TABLE_LIST *t)
thd Thread handle
lex LEX for this thread
unit node that contains all SELECT's for derived tables
t TABLE_LIST for the upper SELECT
IMPLEMENTATION
Derived table is resolved with temporary table. It is created based on the
queries defined. After temporary table is created, 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.
After table creation, the above TABLE_LIST is updated with a new table.
This function is called before any command containing derived table
is executed.
Derived tables is stored in thd->derived_tables and freed in
close_thread_tables()
RETURN
0 ok
1 Error
-1 Error and error message given
*/
static int mysql_derived(THD *thd, LEX *lex, SELECT_LEX_UNIT *unit,
TABLE_LIST *org_table_list)
{
SELECT_LEX *first_select= unit->first_select();
TABLE *table;
int res;
select_union *derived_result;
bool is_union= first_select->next_select() &&
first_select->next_select()->linkage == UNION_TYPE;
bool is_subsel= first_select->first_inner_unit() ? 1: 0;
SELECT_LEX *save_current_select= lex->current_select;
DBUG_ENTER("mysql_derived");
if (!(derived_result= new select_union(0)))
DBUG_RETURN(1); // out of memory
// st_select_lex_unit::prepare correctly work for single select
if ((res= unit->prepare(thd, derived_result, 0)))
goto exit;
derived_result->tmp_table_param.init();
derived_result->tmp_table_param.field_count= unit->types.elements;
/*
Temp table is created so that it hounours if UNION without ALL is to be
processed
*/
if (!(table= create_tmp_table(thd, &derived_result->tmp_table_param,
unit->types, (ORDER*) 0,
is_union && unit->union_distinct, 1,
(first_select->options | thd->options |
TMP_TABLE_ALL_COLUMNS),
HA_POS_ERROR,
org_table_list->alias)))
{
res= -1;
goto exit;
}
derived_result->set_table(table);
/*
if it is preparation PS only then we do not need real data and we
can skip execution (and parameters is not defined, too)
*/
if (!thd->only_prepare())
{
if (is_union)
{
// execute union without clean up
if (!(res= unit->prepare(thd, derived_result, SELECT_NO_UNLOCK)))
res= unit->exec();
}
else
{
unit->offset_limit_cnt= first_select->offset_limit;
unit->select_limit_cnt= first_select->select_limit+
first_select->offset_limit;
if (unit->select_limit_cnt < first_select->select_limit)
unit->select_limit_cnt= HA_POS_ERROR;
if (unit->select_limit_cnt == HA_POS_ERROR)
first_select->options&= ~OPTION_FOUND_ROWS;
lex->current_select= first_select;
res= mysql_select(thd, &first_select->ref_pointer_array,
(TABLE_LIST*) 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 *) first_select->order_list.first,
(ORDER *) first_select->group_list.first,
first_select->having, (ORDER*) NULL,
(first_select->options | thd->options |
SELECT_NO_UNLOCK),
derived_result, unit, first_select);
}
}
if (!res)
{
/*
Here we entirely fix both TABLE_LIST and list of SELECT's as
there were no derived tables
*/
if (derived_result->flush())
res= 1;
else
{
org_table_list->real_name= table->real_name;
org_table_list->table= table;
if (org_table_list->table_list)
{
org_table_list->table_list->real_name= table->real_name;
org_table_list->table_list->table= table;
}
table->derived_select_number= first_select->select_number;
table->tmp_table= TMP_TABLE;
#ifndef NO_EMBEDDED_ACCESS_CHECKS
table->grant.privilege= SELECT_ACL;
#endif
org_table_list->db= (char *)"";
// Force read of table stats in the optimizer
table->file->info(HA_STATUS_VARIABLE);
}
if (!lex->describe)
unit->cleanup();
if (res)
free_tmp_table(thd, table);
else
{
/* Add new temporary table to list of open derived tables */
table->next= thd->derived_tables;
thd->derived_tables= table;
}
exit:
delete derived_result;
lex->current_select= save_current_select;
}
DBUG_RETURN(res);
}
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