public static ConstantVectorExpression createStruct(int outputColumnNum, Object value,
      TypeInfo outputTypeInfo)
          throws HiveException {
    ConstantVectorExpression result = new ConstantVectorExpression(outputColumnNum, outputTypeInfo);
    result.setStructValue(value);
    return result;
  }
Constant is represented as a vector with repeating values.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/ConstantVectorExpression.java