@Override
  public Object[] getAt(int i) throws HiveException {
    RowPositionInBatch rp = getPosition(i);
    return getOrderingValuesFromRow(bufferedBatches.get(rp.batchIndex), rp.rowIndexInBatch);
  }
Finds and element by a partition-level row index. This search can use per-batch indices.
Overrides PTFPartition.getAt() but here in the vectorized codepath (as opposed to
non-vectorized case), getAt only returns the ordering columns. This is because most of the time
getAt is used heavily for range scanning where only the ordering columns are needed. As
VectorizedRowBatch maintains columns, extracting a full row needs more computational effort
than just 1-2 ordering columns. Accessing a random element is possible via getValue(row, col).
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorPTFGroupBatches.java