code: static int fillRows(Row[] rows, TypeDescription schema, VectorizedRowBatch batch, int[] selectedFields) {
  
  		int rowsToRead = Math.min((int) batch.count(), rows.length);
  
  		List<TypeDescription> fieldTypes = schema.getChildren();
  		// read each selected field
  		for (int fieldIdx = 0; fieldIdx < selectedFields.length; fieldIdx++) {
  			int orcIdx = selectedFields[fieldIdx];
  			readField(rows, fieldIdx, fieldTypes.get(orcIdx), batch.cols[orcIdx], rowsToRead);
  		}
  		return rowsToRead;
  	}
docs: Fills an ORC batch into an array of Row.
  
  @param rows The batch of rows need to be filled.
  @param schema The schema of the ORC data.
  @param batch The ORC data.
  @param selectedFields The list of selected ORC fields.
  @return The number of rows that were filled.