dc
f8f65681e1
Review feedback: the first version left targetds out for every filter without derived variables, which silently changed the plain-dataset path to whatever mp_filterstore defaults to. It is now passed exactly as before unless the libds is a format catalog - the one case mp_filterstore has to rewrite itself. The catalog test no longer writes to the statement file: it reads one record from it instead, so -1 means the file could not be opened and 0 means mpe_derived left it empty, which is the claim the branch makes.