@Override
    public void reset() {
      super.reset();
      if (columnVectors == null) return;
      Arrays.fill(columnVectors, null);
    }
Same as columnData, but for the data that already comes as VRBs.
The combination of the two contains all the necessary data,
ql/src/java/org/apache/hadoop/hive/ql/io/orc/encoded/Reader.java