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From 林武康 <>
Subject 答复: RDD usage
Date Tue, 25 Mar 2014 01:45:42 GMT
Hi hequn, a relative question, is that mean the memory usage will doubled? And further more,
if the compute function in a rdd is not idempotent, rdd will changed during the job running,
is that right? 

发件人: "hequn cheng" <>
发送时间: ‎2014/‎3/‎25 9:35
收件人: "" <>
主题: Re: RDD usage

points.foreach(p=>p.y = another_value) will return a new modified RDD. 

2014-03-24 18:13 GMT+08:00 Chieh-Yen <>:

Dear all,

I have a question about the usage of RDD.
I implemented a class called AppDataPoint, it looks like:

case class AppDataPoint(input_y : Double, input_x : Array[Double]) extends Serializable {
  var y : Double = input_y
  var x : Array[Double] = input_x
Furthermore, I created the RDD by the following function.

def parsePoint(line: String): AppDataPoint = {
  /* Some related works for parsing */

Assume the RDD called "points":

val lines = sc.textFile(inputPath, numPartition)
var points = _).cache()

The question is that, I tried to modify the value of this RDD, the operation is:

points.foreach(p=>p.y = another_value)

The operation is workable.
There doesn't have any warning or error message showed by the system and the results are right.
I wonder that if the modification for RDD is a correct and in fact workable design.
The usage web said that the RDD is immutable, is there any suggestion?

Thanks a lot.

Chieh-Yen Lin
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