Comment 5 for bug 951937

Sure, one can expect that t1a.b will have the wrong value: it is not in
subquery's select list, and we're referring to it from outside the SJM nest.

The question is why we're doing that. The clause

  (t1a.b >= t1a.a OR t1b.b = 'z')

was originally inside the subquery, and has been attached to the subquery's
table. Why do we see parts of it attached to outside table...