Eng 6012 inexists sp

I see how we would want to reset hasMatchingTuple to false in the case of non-0 offset, but I'd prefer to explicitly do just that and otherwise let it normally transition from its initial false to true. IMO that would be just a little clearer.

Do we have a similar but possibly worse issue around the setting of hasNullTuple? Consider

    select * from R1 where R1.A NOT IN (select B from R2 order by B limit 1 offset 1);

when R1.A has value {1} and R2.B has values {null, 2}.
I would expect the OFFSET to eliminate the null row so that the query amounts to (WHERE 1 NOT IN {2}) which is TRUE but would eval to NULL as currently implemented.