public void set(TimestampLocalTZWritable t) {
    if (t.bytesEmpty) {
      set(t.getTimestampTZ());
    } else if (t.currentBytes == t.externalBytes) {
      set(t.currentBytes, t.offset, t.timeZone);
    } else {
      set(t.currentBytes, 0, t.timeZone);
    }
  }
true if data is stored in timestamptz field rather than byte arrays.
allows for lazy conversion to bytes when necessary
false otherwise
serde/src/java/org/apache/hadoop/hive/serde2/io/TimestampLocalTZWritable.java