THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
...
R4'. On top of J1, a GroupByOperaptor G1 is added where the group-by key is the primary key of O1 and the subplan input operator and the nested query plan for aggregation is the nested pipeline on top of J1 (with a not-null-filter added).
R5'. All other NestedTupleSourceOperators in the subplan is inlined with a deep copy of the query plan rooted at O1.
...