The executing code had a safety assertion so that it refused to free Items
that it didn't create. However, there is a case, undefined user variables,
which would put Items into the list to be freed.
Instead, do something that is more risky in expectation that the code will
be refactored soon, as Kostja wants to do: Remove the assertions from
prepare() and execute(). Put one assertion at a higher level, before
stmt->set_params_from_vars(), which may then create new to-be-freed Items .
mysql-test/r/ps_11bugs.result:
Create tests to prove that undefined variables work, as keys and not, and
that variables explicitly assigned to Null work.
mysql-test/t/ps_11bugs.test:
Create tests to prove that undefined variables work, as keys and not, and
that variables explicitly assigned to Null work.
sql/sql_prepare.cc:
Move a safety assertion up one level and higher, because there is
legitimately a case where thd->free_list is not NULL going into
Prepared_statement::{prepare,execute} methods.
Kostja plans to refactor this code so that it is both safe and works.
(Now it works, but isn't very safe.)
In the code that converts IN predicates to EXISTS predicates it is changing
the select list elements to constant 1. Example :
SELECT ... FROM ... WHERE a IN (SELECT c FROM ...)
is transformed to :
SELECT ... FROM ... WHERE EXISTS (SELECT 1 FROM ... HAVING a = c)
However there can be no FROM clause in the IN subquery and it may not be
a simple select : SELECT ... FROM ... WHERE a IN (SELECT f(..) AS
c UNION SELECT ...) This query is transformed to : SELECT ... FROM ...
WHERE EXISTS (SELECT 1 FROM (SELECT f(..) AS c UNION SELECT ...)
x HAVING a = c) In the above query c in the HAVING clause is made to be
an Item_null_helper (a subclass of Item_ref) pointing to the real
Item_field (which is not referenced anywhere else in the query anymore).
This is done because Item_ref_null_helper collects information whether
there are NULL values in the result. This is OK for directly executed
statements, because the Item_field pointed by the Item_null_helper is
already fixed when the transformation is done. But when executed as
a prepared statement all the Item instances are "un-fixed" before the
recompilation of the prepared statement. So when the Item_null_helper
gets fixed it discovers that the Item_field it points to is not fixed
and issues an error. The remedy is to keep the original select list
references when there are no tables in the FROM clause. So the above
becomes : SELECT ... FROM ... WHERE EXISTS (SELECT c FROM (SELECT f(..)
AS c UNION SELECT ...) x HAVING a = c) In this way c is referenced
directly in the select list as well as by reference in the HAVING
clause. So it gets correctly fixed even with prepared statements. And
since the Item_null_helper subclass of Item_ref_null_helper is not used
anywhere else it's taken out.
mysql-test/r/ps_11bugs.result:
Test case for the bug
mysql-test/r/subselect.result:
Explain updated because of the tranformation
mysql-test/t/ps_11bugs.test:
Testcase for the bug
sql/item.cc:
Taking out Item_null_helper as it's no longer needed
sql/item.h:
Taking out Item_null_helper as it's no longer needed
sql/item_subselect.cc:
The described change to the IN->EXISTS transformation
test for bug#1180 changed to table naming scheme 't#'.
mysql-test/r/ps_11bugs.result:
Expected results of new tests for bug#1644 and bug#1676,
test for bug#1180 changed to table naming scheme 't#'.
mysql-test/t/ps_11bugs.test:
New tests to check bug#1644 and bug#1676,
test for bug#1180 changed to table naming scheme 't#'.
mysql-test/r/ps_11bugs.result:
Expected results of the added tests for bug#1644 and bug#1676.
mysql-test/t/ps_11bugs.test:
Added tests for bug#1644 and bug#1676,
also minor comments.
- 'ps_10nestset' uses a "nested set" approach for an employee
hierarchy, then does arithmetic on the "salary" field;
(soon) to be extended by inserts / deletes which imply
mass updates on the "l"/"r" fields showing the set inclusion,
- 'ps_11bugs' will get (some of ?) those bug DB entries which
refer to prepared statements, but whose number does not appear
in a test file comment - so it will also be extended.
