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Fixed bug #24653.

Browse Source 
The bug report has demonstrated the following two problems.
1. If an ORDER/GROUP BY list includes a constant expression being 
optimized away and, at the same time, containing single-row
subselects that return more that one row, no error is reported.
Strictly speaking the standard allows to ignore error in this case.
Yet, now a corresponding fatal error is reported in this case.
2. If a query requires sorting by expressions containing single-row
subselects that, however, return more than one row, then the execution
of the query may cause a server crash. 
To fix this some code has been added that blocks execution of a subselect
item in case of a fatal error in the method Item_subselect::exec.
This commit is contained in:
igor@olga.mysql.com
2007-01-25 18:44:35 -08:00
parent 9659c11b6e
commit 36df33d80a
10 changed files with 174 additions and 5 deletions
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74
mysql-test/r/subselect.result
View File

@ -3026,3 +3026,77 @@ id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
DROP TABLE t1;
CREATE TABLE t1 (a int);
INSERT INTO t1 VALUES (2), (4), (1), (3);
CREATE TABLE t2 (b int, c int);
INSERT INTO t2 VALUES
(2,1), (1,3), (2,1), (4,4), (2,2), (1,4);
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2 );
a
2
4
1
3
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1);
ERROR 21000: Subquery returns more than 1 row
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2), a;
a
1
2
3
4
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1), a;
ERROR 21000: Subquery returns more than 1 row
SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 2);
b MAX(c)
1 4
2 2
4 4
SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 1);
ERROR 21000: Subquery returns more than 1 row
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 2),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
a
1
2
3
4
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 1),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
ERROR 21000: Subquery returns more than 1 row
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
a
4
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b)) > 3;
ERROR 21000: Subquery returns more than 1 row
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 2),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
a
2
4
1
3
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 1),
(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
ERROR 21000: Subquery returns more than 1 row
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
a
2
1
3
4
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
ERROR 21000: Subquery returns more than 1 row
DROP TABLE t1,t2;

59
mysql-test/t/subselect.test
View File

@ -1993,4 +1993,63 @@ SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
EXPLAIN SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
DROP TABLE t1;
#
# Bug 24653: sorting by expressions containing subselects
# that return more than one row
#
CREATE TABLE t1 (a int);
INSERT INTO t1 VALUES (2), (4), (1), (3);
CREATE TABLE t2 (b int, c int);
INSERT INTO t2 VALUES
(2,1), (1,3), (2,1), (4,4), (2,2), (1,4);
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2 );
--error 1242
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1);
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 2), a;
--error 1242
SELECT a FROM t1 ORDER BY (SELECT c FROM t2 WHERE b > 1), a;
SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 2);
--error 1242
SELECT b, MAX(c) FROM t2 GROUP BY b, (SELECT c FROM t2 WHERE b > 1);
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 2),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
--error 1242
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 1),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b)) > 3;
--error 1242
SELECT a FROM t1 GROUP BY a
HAVING IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b)) > 3;
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 2),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
--error 1242
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 1),
(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 2 ORDER BY b));
--error 1242
SELECT a FROM t1
ORDER BY IFNULL((SELECT b FROM t2 WHERE b > 4),
(SELECT c FROM t2 WHERE c=a AND b > 1 ORDER BY b));
DROP TABLE t1,t2;
# End of 4.1 tests

6
sql/filesort.cc
View File

@ -387,7 +387,8 @@ static ha_rows find_all_keys(SORTPARAM *param, SQL_SELECT *select,
byte *ref_pos,*next_pos,ref_buff[MAX_REFLENGTH];
my_off_t record;
TABLE *sort_form;
volatile my_bool *killed= &current_thd->killed;
THD *thd= current_thd;
volatile my_bool *killed= &thd->killed;
handler *file;
DBUG_ENTER("find_all_keys");
DBUG_PRINT("info",("using: %s",(select?select->quick?"ranges":"where":"every row")));
@ -474,6 +475,9 @@ static ha_rows find_all_keys(SORTPARAM *param, SQL_SELECT *select,
}
else
file->unlock_row();
/* It does not make sense to read more keys in case of a fatal error */
if (thd->net.report_error)
DBUG_RETURN(HA_POS_ERROR);
}
(void) file->extra(HA_EXTRA_NO_CACHE); /* End cacheing of records */
if (!next_pos)

1
sql/item.cc
View File

@ -47,6 +47,7 @@ Item::Item():
collation.set(&my_charset_bin, DERIVATION_COERCIBLE);
name= 0;
decimals= 0; max_length= 0;
with_subselect= 0;
/* Put item in free list so that we can free all items at end */
THD *thd= current_thd;

3
sql/item.h
View File

@ -142,6 +142,9 @@ public:
my_bool with_sum_func;
my_bool fixed; /* If item fixed with fix_fields */
DTCollation collation;
my_bool with_subselect; /* If this item is a subselect or some
of its arguments is or contains a
subselect */
// alloc & destruct is done as start of select using sql_alloc
Item();

7
sql/item_cmpfunc.cc
View File

@ -2139,6 +2139,7 @@ Item_cond::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
and_tables_cache&= tmp_table_map;
const_item_cache&= item->const_item();
with_sum_func= with_sum_func || item->with_sum_func;
with_subselect|= item->with_subselect;
if (item->maybe_null)
maybe_null=1;
}
@ -2351,7 +2352,7 @@ longlong Item_func_isnull::val_int()
Handle optimization if the argument can't be null
This has to be here because of the test in update_used_tables().
*/
if (!used_tables_cache)
if (!used_tables_cache && !with_subselect)
return cached_value;
return args[0]->is_null() ? 1: 0;
}
@ -2360,7 +2361,7 @@ longlong Item_is_not_null_test::val_int()
{
DBUG_ASSERT(fixed == 1);
DBUG_ENTER("Item_is_not_null_test::val_int");
if (!used_tables_cache)
if (!used_tables_cache && !with_subselect)
{
owner->was_null|= (!cached_value);
DBUG_PRINT("info", ("cached :%d", cached_value));
@ -2387,7 +2388,7 @@ void Item_is_not_null_test::update_used_tables()
else
{
args[0]->update_used_tables();
if (!(used_tables_cache=args[0]->used_tables()))
if (!(used_tables_cache=args[0]->used_tables()) && !with_subselect)
{
/* Remember if the value is always NULL or never NULL */
cached_value= (longlong) !args[0]->is_null();

3
sql/item_cmpfunc.h
View File

@ -843,7 +843,8 @@ public:
else
{
args[0]->update_used_tables();
if ((const_item_cache= !(used_tables_cache= args[0]->used_tables())))
if ((const_item_cache= !(used_tables_cache= args[0]->used_tables())) &&
!with_subselect)
{
/* Remember if the value is always NULL or never NULL */
cached_value= (longlong) args[0]->is_null();

1
sql/item_func.cc
View File

@ -177,6 +177,7 @@ Item_func::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
used_tables_cache|= item->used_tables();
not_null_tables_cache|= item->not_null_tables();
const_item_cache&= item->const_item();
with_subselect|= item->with_subselect;
}
}
fix_length_and_dec();

4
sql/item_subselect.cc
View File

@ -39,6 +39,7 @@ Item_subselect::Item_subselect():
engine(0), old_engine(0), used_tables_cache(0), have_to_be_excluded(0),
const_item_cache(1), engine_changed(0), changed(0)
{
with_subselect= 1;
reset();
/*
item value is NULL if select_subselect not changed this value
@ -201,6 +202,9 @@ bool Item_subselect::exec()
mem root
*/
thd->mem_root= &thd->main_mem_root;
if (thd->net.report_error)
/* Do not execute subselect in case of a fatal error */
return 1;
res= engine->exec();
thd->mem_root= old_root;

21
sql/sql_select.cc
View File

@ -644,6 +644,13 @@ JOIN::optimize()
{
ORDER *org_order= order;
order=remove_const(this, order,conds,1, &simple_order);
if (thd->net.report_error)
{
error= 1;
DBUG_PRINT("error",("Error from remove_const"));
DBUG_RETURN(1);
}
/*
If we are using ORDER BY NULL or ORDER BY const_expression,
return result in any order (even if we are using a GROUP BY)
@ -747,6 +754,12 @@ JOIN::optimize()
group_list= remove_const(this, (old_group_list= group_list), conds,
rollup.state == ROLLUP::STATE_NONE,
&simple_group);
if (thd->net.report_error)
{
error= 1;
DBUG_PRINT("error",("Error from remove_const"));
DBUG_RETURN(1);
}
if (old_group_list && !group_list)
select_distinct= 0;
}
@ -763,6 +776,12 @@ JOIN::optimize()
{
group_list= procedure->group= remove_const(this, procedure->group, conds,
1, &simple_group);
if (thd->net.report_error)
{
error= 1;
DBUG_PRINT("error",("Error from remove_const"));
DBUG_RETURN(1);
}
calc_group_buffer(this, group_list);
}
@ -4428,6 +4447,8 @@ remove_const(JOIN *join,ORDER *first_order, COND *cond,
*simple_order=0; // Must do a temp table to sort
else if (!(order_tables & not_const_tables))
{
if (order->item[0]->with_subselect)
order->item[0]->val_str(&order->item[0]->str_value);
DBUG_PRINT("info",("removing: %s", order->item[0]->full_name()));
continue; // skip const item
}