@Override
  public void evaluate(VectorizedRowBatch vrg) {
    if (!initialized) {
      initValue();
    }

    switch (type) {
    case LONG:
      evaluateLong(vrg);
      break;
    case DOUBLE:
      evaluateDouble(vrg);
      break;
    case BYTES:
      evaluateBytes(vrg);
      break;
    case DECIMAL:
      evaluateDecimal(vrg);
      break;
    case TIMESTAMP:
      evaluateTimestamp(vrg);
      break;
    case INTERVAL_DAY_TIME:
      evaluateIntervalDayTime(vrg);
      break;
    default:
      throw new IllegalStateException("Unsupported type " + type);
    }
  }
Constant is represented as a vector with repeating values.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/DynamicValueVectorExpression.java