How to add a new column to a Spark RDD?

问题:

I have a RDD with MANY columns (e.g., hundreds), how do I add one more column at the end of this RDD?

For example, if my RDD is like below:

    123, 523, 534, ..., 893
    536, 98, 1623, ..., 98472
    537, 89, 83640, ..., 9265
    7297, 98364, 9, ..., 735
    ......
    29, 94, 956, ..., 758

how can I add a column to it, whose value is the sum of the second and the third columns?

Thank you very much.

回答1:

You do not have to use Tuple* objects at all for adding a new column to an RDD.

It can be done by mapping each row, taking its original contents plus the elements you want to append, for example:

val rdd = ...
val withAppendedColumnsRdd = rdd.map(row => {
  val originalColumns = row.toSeq.toList
  val secondColValue = originalColumns(1).asInstanceOf[Int]
  val thirdColValue = originalColumns(2).asInstanceOf[Int]
  val newColumnValue = secondColValue + thirdColValue 
  Row.fromSeq(originalColumns :+ newColumnValue)
  // Row.fromSeq(originalColumns ++ List(newColumnValue1, newColumnValue2, ...)) // or add several new columns
})

回答2:

you have RDD of tuple 4, apply map and convert it to tuple5

val rddTuple4RDD = ...........
val rddTuple5RDD = rddTuple4RDD.map(r=> Tuple5(rddTuple4._1, rddTuple4._2, rddTuple4._3, rddTuple4._4, rddTuple4._2 + rddTuple4._3))