Bug#13012483:EXPLAIN EXTENDED, PREPARED STATEMENT, CRASH IN

CHECK_SIMPLE_EQUALITY

PROBLEM:
Crash in "check_simple_equality" when using a subquery with "IN" and
"ALL" in prepare.

ANALYSIS:
Crash can be reproduced using a simplified query like this one:
prepare s from "select 1 from g1 where 1 < all (
                select @:=(1 in (select 1 from g1)) from g1)";

This bug is currently present only on 5.5.and 5.1. Its fixed as part
of work log(#1110) in 5.6. We are taking one change to fix this
in 5.5 and 5.1.

Problem seems to be present because we are trying to evaluate "is_null"
on an argument which is part of a subquery
(In Item_is_not_null_test::update_used_tables()).
But the condition to evaluate is only when we do not have a sub query
present, which means to say that "with_subselect" is not set.
With respect to the above query, we create an object of type
"Item_in_optimizer" which by definition is always associated with a
subquery. While in 5.6 we set "with_subselect" to true for
"Item_in_optimizer" object, we do not do the same in 5.5. This results in
the evaluation for "is_null" resulting in a coredump.
So, we are now setting "with_subselect" to true for "Item_in_optimizer"
in 5.1 and 5.5.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index 4d8cadfcce9..b185bf02790 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -254,7 +254,7 @@ public:
   Item_in_optimizer(Item *a, Item_in_subselect *b):
     Item_bool_func(a, my_reinterpret_cast(Item *)(b)), cache(0),
     save_cache(0), result_for_null_param(UNKNOWN)
-  {}
+  { with_subselect= true; }
   bool fix_fields(THD *, Item **);
   bool fix_left(THD *thd, Item **ref);
   bool is_null();