Re: remove_useless_joins vs. bug #19560

...For completeness the definition of u here is like so:

CREATE TABLE u (id int PRIMARY KEY, a int);
INSERT INTO u (id, a) VALUES
(1, 1),
(2, 2),
(3, 3),
(4, 0),
(5, 1),
(6, 2),
(7, 3),
(8, 0),
(9, 1),
(10, 2);