How to create pair rdd in spark
How do you make a paired RDD?
Again, here using the first word as the keyword to create a Spark paired RDD,
- PairFunction<String, String, String> keyData =
- new PairFunction<String, String, String>() {
- public Tuple2<String, String> call(String x) {
- return new Tuple2(x. split(” “)[0], x);
- JavaPairRDD<String, String> pairs = lines. mapToPair(keyData)
What is paired RDD in spark?
Paired RDD is a distributed collection of data with the key-value pair. It is a subset of Resilient Distributed Dataset So it has all the features of RDD and some new feature for the key-value pair. There are many transformation operations available for Paired RDD.
How do I join two RDD in spark?
Which function in spark is used to combine two RDDs by keys
- rdd1 = [ (key1, [value1, value2]), (key2, [value3, value4]) ]
- rdd2 = [ (key1, [value5, value6]), (key2, [value7]) ]
- ret = [ (key1, [value1, value2, value5, value6]), (key2, [value3, value4, value7]) ]
What is the difference between RDDs and paired RDDs?
The Pair RDD that you end up with allows you to reduce values or to sort data based on the key, to name a few examples. For example, pair RDDs have a reduceByKey() method that can aggregate data separately for each key, and a join() method that can merge two RDDs together by grouping elements with the same key.
What is spark mapValues?
mapValues is only applicable for PairRDDs, meaning RDDs of the form RDD[(A, B)] . In that case, mapValues operates on the value only (the second part of the tuple), while map operates on the entire record (tuple of key and value).
What is spark collectAsMap?
collectAsMap ()[source] Return the key-value pairs in this RDD to the master as a dictionary. Notes. This method should only be used if the resulting data is expected to be small, as all the data is loaded into the driver’s memory.