@Override
    public ScanType getScanType(CompactionRequestImpl request) {
      return request.isAllFiles() ? COMPACT_DROP_DELETES : COMPACT_RETAIN_DELETES;
    }
Creates file scanners for compaction.
@param filesToCompact Files.
@return Scanners.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/compactions/Compactor.java