TimestampOfValue.scala

 val result = stRdd.groupBy(_.id).map({
  case (ig, vars) =>
    val svars: Seq[SomeTable] = vars.toSeq.sortBy(_.updateAt).reverse

    def ex(f: SomeTable => String): String = svars.map(f).find(_ != null).orNull

    def ex2(f: SomeTable => String): (String, Timestamp) = {
      svars.map(x => (f(x), x.updateAt)).find(_._1 != null).getOrElse((null, null))
    }

    def max[T: Ordering](f: SomeTable => T): T = svars.map(f).max

    val (ex1, ex_dt) = ex2(_.value2)
    (SomeTable(id = ig, value1 = ex(_.value1),
      value2 = ex1,
      updateAt = max(_.updateAt),
      value3 = max(_.value3),
      value4 = ex(_.value4)), ex_dt)
})