private void throwIOException(int i, Throwable t) throws IOException {
    LOG.error("Error at row " + rowInBatch + "/" + batch.size + ", column " + i
        + "/" + schema.size() + " " + batch.cols[i], t);
    throw (t instanceof IOException) ? (IOException) t : new IOException(t);
  }
Wrapper class to map a virtual column to a handler defined by subclasses of {@link BatchToRowReader}.
The handler should be a set operation which sets the value of the virtual column value
in the current row.
ql/src/java/org/apache/hadoop/hive/ql/io/BatchToRowReader.java