public ColumnStreamData[] getColumnData(int colIx) {
    if (!hasData[colIx]) throw new AssertionError("No data for column " + colIx);
    return columnData[colIx];
  }
Indicates which columns have data. This is indexed by the column ID in ORC file schema;
the indices that are not included will not have data. Correspond to columnData elements.
storage-api/src/java/org/apache/hadoop/hive/common/io/encoded/EncodedColumnBatch.java