Thanks Reynold for the reason as to why sortBykey invokes a Job
When you say "DataFrame/Dataset does not have this issue" is it right to
assume you are referring to Spark 2.0 or Spark 1.6 DF already has built-in
it?
Thanking You
---------------------------------------------------------------------------------
Praveen Devarao
Spark Technology Centre
IBM India Software Labs
---------------------------------------------------------------------------------
"Courage doesn't always roar. Sometimes courage is the quiet voice at the
end of the day saying I will try again"
From: Reynold Xin <r...@databricks.com>
To: Praveen Devarao/India/IBM@IBMIN
Cc: "dev@spark.apache.org" <dev@spark.apache.org>, user
<u...@spark.apache.org>
Date: 25/04/2016 11:26 am
Subject: Re: Do transformation functions on RDD invoke a Job
[sc.runJob]?
Usually no - but sortByKey does because it needs the range boundary to be
built in order to have the RDD. It is a long standing problem that's
unfortunately very difficult to solve without breaking the RDD API.
In DataFrame/Dataset we don't have this issue though.
On Sun, Apr 24, 2016 at 10:54 PM, Praveen Devarao <praveen...@in.ibm.com>
wrote:
Hi,
I have a streaming program with the block as below [ref:
https://github.com/agsachin/streamingBenchmark/blob/master/spark-benchmarks/src/main/scala/TwitterStreaming.scala
]
1 val lines = messages.map(_._2)
2 val hashTags = lines.flatMap(status => status.split(" "
).filter(_.startsWith("#")))
3 val topCounts60 = hashTags.map((_, 1)).reduceByKey( _ + _ )
3a .map { case (topic, count) => (count, topic) }
3b .transform(_.sortByKey(false))
4atopCounts60.foreachRDD( rdd => {
4b val topList = rdd.take( 10 )
})
This batch is triggering 2 jobs...one at line 3b(sortByKey) and
the other at 4b (rdd.take) I agree that there is a Job triggered on line
4b as take() is an action on RDD while as on line 3b sortByKey is just a
transformation function which as per docs is lazy evaluation...but I see
that this line uses a RangePartitioner and Rangepartitioner on
initialization invokes a method called sketch() that invokes collect()
triggering a Job.
My question: Is it expected that sortByKey will invoke a Job...if
yes, why is sortByKey listed as a transformation and not action. Are there
any other functions like this that invoke a Job, though they are
transformations and not actions?
I am on Spark 1.6
Thanking You
---------------------------------------------------------------------------------
Praveen Devarao
Spark Technology Centre
IBM India Software Labs
---------------------------------------------------------------------------------
"Courage doesn't always roar. Sometimes courage is the quiet voice at the
end of the day saying I will try again"
