public List<Path> getObsolete() {
    return obsolete;
  }
Get the list of obsolete directories. After filtering out bases and
deltas that are not selected by the valid transaction/write ids list, return the
list of original files, bases, and deltas that have been replaced by
more up to date ones.  Not {@code null}.
ql/src/java/org/apache/hadoop/hive/ql/io/AcidDirectory.java