Added test cases for bug #7351.
item_cmpfunc.cc:
Fixed bug #7351: incorrect result for a query with a
subquery returning empty set.
If in the predicate v IN (SELECT a FROM t WHERE cond)
v is null, then the result of the predicate is either
INKNOWN or FALSE. It is FALSE if the subquery returns
an empty set.
item_subselect.cc:
Fixed bug #7351: incorrect result for a query with a
subquery returning empty set.
The problem was due to not a quite legal transformation
for 'IN' subqueries. A subquery containing a predicate
of the form
v IN (SELECT a FROM t WHERE cond)
was transformed into
EXISTS(SELECT a FROM t WHERE cond AND (a=v OR a IS NULL)).
Yet, this transformation is valid only if v is not null.
If v is null, then, in the case when
(SELECT a FROM t WHERE cond) returns an empty set the value
of the predicate is FALSE, otherwise the result of the
predicate is INKNOWN.
The fix resolves this problem by changing the result
of the transformation to
EXISTS(SELECT a FROM t WHERE cond AND (v IS NULL OR (a=v OR a IS NULL)))
in the case when v is nullable.
The new transformation prevents applying the lookup
optimization for IN subqueries. To make it still
applicable we have to introduce guarded access methods.
(back to behaviour of 4.1.7). Warning was not fatal: mysqldump continued. And the good thing is that it helped spot that starting from 4.1.7,
SHOW CREATE DATABASE failed (if --single-transaction and first db has non-empty InnoDB table and there is a second db) and thus mysqldump
produced CREATE DATABASE statements missing the CHARACTER SET clause. Removing the bug which was in the server, and the warning reporting in
mysqldump (compatibility with old servers).
For numeric constants we only need to add, since the parser doesn't produce
negative numbers.
For strings we only add (we actually could substract 1 if given string is a constant
and it has '-number' form but we're not doing that because
* we set max_length bigger then necessary in other cases as well.
* the current solution is simpler and safer (bigger max_length is better then cutting out)
which Heikki fixed in 4.1.8 and 4.0.23. I verified that without Heikki's patch the test fails (7 gets inserted).
Test added to 4.1 because in testsuite of 4.0 it's impossible to start slave with InnoDB.
In Item_ref::Item_ref set maybe_null (and other fields fix_fields sets) to be the
same as in (*ref), because Item_ref::fix_fields() will not be called. Previously
maybe_null was 0 always and this produced a bogus state where
maybe_null==0 && is_null() == true
which broke evaluation for some upper-level Items, like AND and OR.
tables requires privileges for them if some table or column level grants
present" (with after-review fixes).
We should set SELECT_ACL for implicitly opened tables in
my_tz_check_n_skip_implicit_tables() to be able to bypass privilege
checking in check_grant(). Also we should exclude those tables from
privilege checking in multi-update.
