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mariadb/sql/sql_union.cc

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/* 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, SELECT_NO_UNLOCK)))
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)
{
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;
}
/*
initialization procedures before fake_select_lex preparation()
SYNOPSIS
st_select_lex_unit::init_prepare_fake_select_lex()
thd - thread handler
RETURN
options of SELECT
*/
ulong
st_select_lex_unit::init_prepare_fake_select_lex(THD *thd)
{
ulong options_tmp= thd->options | fake_select_lex->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_tmp&= ~OPTION_FOUND_ROWS;
else if (found_rows_for_union && !thd->lex->describe)
options_tmp|= OPTION_FOUND_ROWS;
fake_select_lex->ftfunc_list_alloc.empty();
fake_select_lex->ftfunc_list= &fake_select_lex->ftfunc_list_alloc;
fake_select_lex->table_list.link_in_list((byte *)&result_table_list,
(byte **)
&result_table_list.next);
return options_tmp;
}
int st_select_lex_unit::prepare(THD *thd_arg, select_result *sel_result,
ulong additional_options)
{
SELECT_LEX *lex_select_save= thd_arg->lex->current_select;
SELECT_LEX *sl, *first_select;
select_result *tmp_result;
DBUG_ENTER("st_select_lex_unit::prepare");
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_select_in_union(); sl; sl= sl->next_select())
{
sl->join->result= result;
select_limit_cnt= HA_POS_ERROR;
offset_limit_cnt= 0;
if (!sl->join->procedure &&
result->prepare(sl->join->fields_list, this))
{
DBUG_RETURN(1);
}
sl->join->select_options|= SELECT_DESCRIBE;
sl->join->reinit();
}
}
DBUG_RETURN(0);
}
prepared= 1;
res= 0;
thd_arg->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->tmp_table_param.init();
if (describe)
tmp_result= sel_result;
}
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())
{
sl->options|= SELECT_NO_UNLOCK;
JOIN *join= new JOIN(thd_arg, sl->item_list,
sl->options | thd_arg->options | additional_options,
tmp_result);
if (!join)
goto err;
thd_arg->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_arg->is_fatal_error)
goto err;
if (sl == first_select)
{
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(thd_arg, item_tmp));
}
if (thd_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(thd_arg, item_tmp))
DBUG_RETURN(-1);
}
}
}
// it is not single select
if (first_select->next_select())
{
union_result->tmp_table_param.field_count= types.elements;
if (!(table= create_tmp_table(thd_arg,
&union_result->tmp_table_param, types,
(ORDER*) 0, (bool) union_distinct, 1,
(first_select_in_union()->options |
thd_arg->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);
thd_arg->lex->current_select= lex_select_save;
if (!item_list.elements)
{
Statement *stmt= thd->current_statement;
Statement backup;
if (stmt)
thd->set_n_backup_item_arena(stmt, &backup);
Field **field;
for (field= table->field; *field; field++)
{
Item_field *item= new Item_field(*field);
if (!item || item_list.push_back(item))
{
if (stmt)
thd->restore_backup_item_arena(stmt, &backup);
DBUG_RETURN(-1);
}
}
if (stmt)
{
thd->restore_backup_item_arena(stmt, &backup);
/* prepare fake select to initialize it correctly */
ulong options_tmp= init_prepare_fake_select_lex(thd);
if (!(fake_select_lex->join= new JOIN(thd, item_list, thd->options,
result)))
{
fake_select_lex->table_list.empty();
DBUG_RETURN(-1);
}
fake_select_lex->item_list= item_list;
thd_arg->lex->current_select= fake_select_lex;
res= fake_select_lex->join->
prepare(&fake_select_lex->ref_pointer_array,
(TABLE_LIST*) fake_select_lex->table_list.first,
0, 0,
fake_select_lex->order_list.elements,
(ORDER*) fake_select_lex->order_list.first,
(ORDER*) NULL, NULL, (ORDER*) NULL,
fake_select_lex, this);
fake_select_lex->table_list.empty();
}
}
}
else
first_select->braces= 0; // remove our changes
thd_arg->lex->current_select= lex_select_save;
DBUG_RETURN(res || thd_arg->is_fatal_error ? 1 : 0);
err:
thd_arg->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 && !describe)
DBUG_RETURN(0);
executed= 1;
if (uncacheable || !item || !item->assigned() || describe)
{
if (optimized && item)
{
if (item->assigned())
{
item->assigned(0); // We will reinit & rexecute unit
item->reset();
table->file->delete_all_rows();
}
/* re-enabling indexes for next subselect iteration */
if (union_distinct && table->file->enable_indexes(HA_KEY_SWITCH_ALL))
DBUG_ASSERT(1);
}
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 && !describe)
{
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 || describe)
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;
res= sl->join->optimize();
}
if (!res)
{
records_at_start= table->file->records;
sl->join->exec();
if (sl == union_distinct)
{
if (table->file->disable_indexes(HA_KEY_SWITCH_ALL))
DBUG_RETURN(1);
table->no_keyread=1;
}
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_tmp= init_prepare_fake_select_lex(thd);
JOIN *join= fake_select_lex->join;
if (!join)
{
/*
allocate JOIN for fake select only once (prevent
mysql_select automatic allocation)
*/
if (!(fake_select_lex->join= new JOIN(thd, item_list, thd->options,
result)))
{
fake_select_lex->table_list.empty();
DBUG_RETURN(-1);
}
/*
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_tmp | SELECT_NO_UNLOCK,
result, this, fake_select_lex);
fake_select_lex->table_list.empty();
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 (cleaned)
{
DBUG_RETURN(0);
}
cleaned= 1;
if (union_result)
{
delete union_result;
union_result=0; // Safety
if (table)
free_tmp_table(thd, table);
table= 0; // Safety
}
JOIN *join;
SELECT_LEX *sl= first_select_in_union();
for (; sl; sl= sl->next_select())
{
if ((join= sl->join))
{
error|= sl->join->cleanup();
delete join;
}
else
{
// it can be DO/SET with subqueries
for (SELECT_LEX_UNIT *lex_unit= sl->first_inner_unit();
lex_unit != 0;
lex_unit= lex_unit->next_unit())
{
error|= lex_unit->cleanup();
}
}
}
if (fake_select_lex && (join= fake_select_lex->join))
{
join->tables_list= 0;
join->tables= 0;
error|= join->cleanup();
delete join;
}
DBUG_RETURN(error);
}
void st_select_lex_unit::reinit_exec_mechanism()
{
prepared= optimized= executed= 0;
#ifndef DBUG_OFF
if (first_select()->next_select())
{
List_iterator_fast<Item> it(item_list);
Item *field;
while ((field= it++))
{
/*
we can't cleanup here, because it broke link to temporary table field,
but have to drop fixed flag to allow next fix_field of this field
during re-executing
*/
field->fixed= 0;
}
}
#endif
}
/*
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
0 - OK
-1 - error
*/
int st_select_lex_unit::change_result(select_subselect *result,
select_subselect *old_result)
{
int res= 0;
for (SELECT_LEX *sl= first_select_in_union(); sl; sl= sl->next_select())
{
if (sl->join && sl->join->result == old_result)
if ((res= sl->join->change_result(result)))
return (res);
}
if (fake_select_lex && fake_select_lex->join)
res= fake_select_lex->join->change_result(result);
return (res);
}
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