public void setStreamData(int colIx, int streamIx, ColumnStreamData csd) {
    assert hasData[colIx];
    columnData[colIx][streamIx] = csd;
  }
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