code: public static int getEffectiveIndexIntervalAfterIndex(int index, int samplingLevel, int minIndexInterval)
      {
          assert index >= 0;
          index %= samplingLevel;
          List<Integer> originalIndexes = getOriginalIndexes(samplingLevel);
          int nextEntryOriginalIndex = (index == originalIndexes.size() - 1) ? BASE_SAMPLING_LEVEL : originalIndexes.get(index + 1);
          return (nextEntryOriginalIndex - originalIndexes.get(index)) * minIndexInterval;
      }
docs: Calculates the effective index interval after the entry at `index` in an IndexSummary.  In other words, this
  returns the number of partitions in the primary on-disk index before the next partition that has an entry in
  the index summary.  If samplingLevel == BASE_SAMPLING_LEVEL, this will be equal to the index interval.
  @param index an index into an IndexSummary
  @param samplingLevel the current sampling level for that IndexSummary
  @param minIndexInterval the min index interval (effective index interval at full sampling)
  @return the number of partitions before the next index summary entry, inclusive on one end