private void copyPartitionColumnToOverflow(Object[] partitionKey) {
    // Set partition column in overflowBatch.
    // We can set by ref since our last batch is held by us.
    final int keyInputColumnCount = keyWithoutOrderColumnMap.length;
    for (int i = 0; i < keyInputColumnCount; i++) {
      final int keyColumnNum = keyWithoutOrderColumnMap[i];
      Preconditions.checkState(overflowBatch.cols[keyColumnNum] != null);
      setRepeatingColumn(partitionKey[i], overflowBatch, keyColumnNum);
    }
  }
Returns the values of ordering columns from a given batch and given row in an Object[].
@param vectorizedRowBatch
@param rowIndexInBatch
@return
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorPTFGroupBatches.java