At present, SlotBasedStageBuilder's constructor has some logic that searches the QuerySolutionNode tree to retrieve some information from the CollectionScanNode (if one exists) prior to SlotBasedStageBuilder::build() being called.

In the future, if we need to gather other information from the QuerySolutionNode tree prior to SlotBasedStageBuilder::build() being called, we should consider adding a formal analysis pass to SlotBasedStageBuilder.