@Override
  public void evaluateGroupBatch(VectorizedRowBatch batch) throws HiveException {

    // We don't evaluate input columns...

    LongColumnVector longColVector = (LongColumnVector) batch.cols[outputColumnNum];
    longColVector.isRepeating = true;
    longColVector.isNull[0] = false;
    longColVector.vector[0] = denseRank;
  }
This class evaluates rank() for a PTF group.

Dense rank starts at 1; the same dense rank is streamed to the output column as repeated; after
the last group row, the dense rank incremented by 1.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/ptf/VectorPTFEvaluatorDenseRank.java