Removing tombsone entries in copycat

[Terry Tan]

Hi Jodan,

The global index only tracks the entries being committed on all servers , when we tried to compact  tombstone entry ,  how do we know all the previous 

related entries had being released , another case ,if the tombstone entry is released ,while the previous related entries is not , will the tombstone be removed in the compact process?

another question?

 for (Long segmentId : segments.keySet()) {

      Segment segment = segments.get(segmentId);

      Map.Entry<Long, Segment> previousEntry = segments.floorEntry(segmentId - 1);

      if (previousEntry != null) {

        Segment previousSegment = previousEntry.getValue();

        if (previousSegment.index() + previousSegment.length() - 1 < segment.index()) {

          previousSegment.skip(segment.index() - (previousSegment.index() + previousSegment.length()));

        }

      }

    }

why do you skip  "the segment.index() - (previousSegment.index() + previousSegment.length()"  ?