@SuppressWarnings("unchecked")
    @Override
    protected void resetColumnArrays(int columnCount) {
      super.resetColumnArrays(columnCount);
      if (columnVectors != null && columnCount == columnVectors.length) {
        Arrays.fill(columnVectors, null);
        return;
      }
      if (columnVectors != null) {
        columnVectors = new List[columnCount];
      } // else just keep it 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