I have an RDD called
JavaPairRDD<String, List<String>> existingRDD;
Now I need to initialize this existingRDD
to empty so that when I get the actual rdd's I can do a union with this existingRDD
.
How do I initialize existingRDD
to an empty RDD except initializing it to null?
Here is my code:
JavaPairRDD<String, List<String>> existingRDD;
if(ai.get()%10==0)
{
existingRDD.saveAsNewAPIHadoopFile("s3://manthan-impala-test/kinesis-dump/" + startTime + "/" + k + "/" + System.currentTimeMillis() + "/",
NullWritable.class, Text.class, TextOutputFormat.class); //on worker failure this will get overwritten
}
else
{
existingRDD.union(rdd);
}
To create an empty RDD in Java, you'll just to do the following:
// Get an RDD that has no partitions or elements.
JavaSparkContext jsc;
...
JavaRDD<T> emptyRDD = jsc.emptyRDD();
I trust you know how to use generics, otherwise, for your case, you'll need:
JavaRDD<Tuple2<String,List<String>>> emptyRDD = jsc.emptyRDD();
JavaPairRDD<String,List<String>> emptyPairRDD = JavaPairRDD.fromJavaRDD(
existingRDD
);
You can also use the mapToPair
method to convert your JavaRDD
to a JavaPairRDD
.
In Scala :
val sc: SparkContext = ???
...
val emptyRDD = sc.emptyRDD
// emptyRDD: org.apache.spark.rdd.EmptyRDD[Nothing] = EmptyRDD[1] at ...
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