@Override
    public String toString() {
      return super.toString() + ", original is set " + (this.originalData != null)
          + ", buffer was replaced " + (originalCbIndex == -1);
    }
CacheChunk that is pre-created for new cache data; initially, it contains an original disk
buffer and an unallocated MemoryBuffer object. Before we expose it, the MB is allocated,
the data is decompressed, and original compressed data is discarded. The chunk lives on in
the DiskRange list created for the request, and everyone treats it like regular CacheChunk.
ql/src/java/org/apache/hadoop/hive/ql/io/orc/encoded/EncodedReaderImpl.java