> If we were to flatten it to a plain "select * from z" then maybe things
> would work all right, but the present implementation treats both WITH
> clauses as equally requiring single evaluation.
Surely it should be a single evaluation for each time that branch of
the upper WITH is recursively evaluated? I can't think what the
semantics are otherwise. a is a function of z, so you can't change
the definition of z and pretend like it's OK that a still has the same
contents as before.
...Robert