SortExec

In WholeStageCodeGen, its doConsume does not call parent's consume (shouldStop never return true), in order to break the link. It means when the child call produce, which will eventually invoke its own doConsume, child never stops until all records are sorted.

In its doProduce, addToSorter is invoked, which sort all child's record. From there, it continuously feeds the sorted record to parents through consume.