protected ArrayList<HStoreFile> getCurrentEligibleFiles(ArrayList<HStoreFile> candidateFiles,
    final List<HStoreFile> filesCompacting) {
    // candidates = all storefiles not already in compaction queue
    if (!filesCompacting.isEmpty()) {
      // exclude all files older than the newest file we're currently
      // compacting. this allows us to preserve contiguity (HBASE-2856)
      HStoreFile last = filesCompacting.get(filesCompacting.size() - 1);
      int idx = candidateFiles.indexOf(last);
      Preconditions.checkArgument(idx != -1);
      candidateFiles.subList(0, idx + 1).clear();
    }
    return candidateFiles;
  }
@param compactionSize Total size of some compaction
@return whether this should be a large or small compaction
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/compactions/SortedCompactionPolicy.java