private void assignDecimalNullsNoRepeatingSelection(int keyIndex, int index, int size,
      DecimalColumnVector columnVector, int[] selected) {
    for(int i = 0; i < size; ++i) {
      int row = selected[i];
      if (!columnVector.isNull[row]) {
        vectorHashKeyWrappers[i].assignDecimal(index, columnVector.vector[row]);
      } else {
        vectorHashKeyWrappers[i].assignNullDecimal(keyIndex, index);
      }
    }
  }
Helper method to assign values from a vector column into the key wrapper.
Optimized for Decimal type, possible nulls, no repeat values, batch selection vector.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/wrapper/VectorHashKeyWrapperBatch.java