Current cumulative point calculate algorithm may skip singleton rowset when the rowset has only one segment and with NONOVERLAPPING flag. When a tablet is new created and cumulate many singleton rowsets, cumulative point will be calculated as the max version + 1, and then cumulative compaction couldn't pick any rowsets and compaction failed, and
will lead the next base compaction on this tablet with all rowsets, which can also cause memory consume problem, suppose there are thousands of rowsets.
All singleton rowsets must be newly wrote by delta writer and hasn't
do any compaction, we should place cumulative point before any of these rowsets.
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