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Fix for bug lp:1006231

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Analysis:

When a subquery that needs a temp table is executed during
the prepare or optimize phase of the outer query, at the end
of the subquery execution all the JOIN_TABs of the subquery
are replaced by a new JOIN_TAB that selects from the temp table.
However that temp table has no corresponding TABLE_LIST.
Once EXPLAIN execution reaches its last phase, it tries to print
the names of the subquery tables through its TABLE_LISTs, but in
the case of this bug there is no such TABLE_LIST (it is NULL),
hence a crash.

Solution:
The fix is to block subquery evaluation inside
Item_func_like::fix_fields and Item_func_like::select_optimize()
using the Item::is_expensive() test.
This commit is contained in:
unknown 2012-05-30 19:10:18 +03:00
parent 662c51bad1
commit 66dfceb11f
3 changed files with 30 additions and 2 deletions
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15
mysql-test/r/subselect_innodb.result
View file

@ -365,4 +365,19 @@ GROUP BY 1
MAX( f1 )
NULL
drop table t1, t2, t3;
#
# LP BUG#1006231 crash in select_describe
#
create table t1(a1 int) ENGINE=InnoDB;
insert into t1 values (1);
explain
select 1 from t1 where 1 like (select 1 from t1 where 1 <=> (select 1 from t1 group by a1));
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 1
2 SUBQUERY t1 ALL NULL NULL NULL NULL 1
3 SUBQUERY t1 ALL NULL NULL NULL NULL 1 Using temporary; Using filesort
select 1 from t1 where 1 like (select 1 from t1 where 1 <=> (select 1 from t1 group by a1));
1
1
drop table t1;
set optimizer_switch=@subselect_innodb_tmp;

12
mysql-test/t/subselect_innodb.test
View file

@ -356,4 +356,16 @@ WHERE f2 >= (
drop table t1, t2, t3;
--echo #
--echo # LP BUG#1006231 crash in select_describe
--echo #
create table t1(a1 int) ENGINE=InnoDB;
insert into t1 values (1);
explain
select 1 from t1 where 1 like (select 1 from t1 where 1 <=> (select 1 from t1 group by a1));
select 1 from t1 where 1 like (select 1 from t1 where 1 <=> (select 1 from t1 group by a1));
drop table t1;
set optimizer_switch=@subselect_innodb_tmp;

5
sql/item_cmpfunc.cc
View file

@ -4656,7 +4656,7 @@ longlong Item_func_like::val_int()
Item_func::optimize_type Item_func_like::select_optimize() const
{
if (args[1]->const_item())
if (args[1]->const_item() && !args[1]->is_expensive())
{
String* res2= args[1]->val_str((String *)&cmp.value2);
const char *ptr2;
@ -4743,7 +4743,8 @@ bool Item_func_like::fix_fields(THD *thd, Item **ref)
We could also do boyer-more for non-const items, but as we would have to
recompute the tables for each row it's not worth it.
*/
if (args[1]->const_item() && !use_strnxfrm(collation.collation))
if (args[1]->const_item() && !use_strnxfrm(collation.collation) &&
!args[1]->is_expensive())
{
String* res2 = args[1]->val_str(&cmp.value2);
if (!res2)