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https://issues.apache.org/jira/browse/SPARK-21025?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16043229#comment-16043229
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Sean Owen commented on SPARK-21025:
-----------------------------------
It's not clear why you're parallelizing 'src' to begin with, or why this is a
simple reproduction. What are the values and sizes of all the intermediate
structures? something else is going wrong here.
> missing data in jsc.union
> -------------------------
>
> Key: SPARK-21025
> URL: https://issues.apache.org/jira/browse/SPARK-21025
> Project: Spark
> Issue Type: Bug
> Components: Java API
> Affects Versions: 2.1.0, 2.1.1
> Environment: Ubuntu 16.04
> Reporter: meng xi
>
> we are using an iterator of RDD for some special data processing, and then
> using union to rebuild a new RDD. we found the result RDD are often empty or
> missing most of the data. Here is a simplified code snippet for this bug:
> SparkConf sparkConf = new
> SparkConf().setAppName("Test").setMaster("local[*]");
> SparkContext sparkContext = SparkContext.getOrCreate(sparkConf);
> JavaSparkContext jsc =
> JavaSparkContext.fromSparkContext(sparkContext);
> JavaRDD<String[]> src = jsc.parallelize(IntStream.range(0,
> 3000).mapToObj(i -> new String[10]).collect(Collectors.toList()));
> Iterator<String[]> it = src.toLocalIterator();
> List<JavaRDD<String[]>> rddList = new LinkedList<>();
> List<String[]> resultBuffer = new LinkedList<>();
> while (it.hasNext()) {
> resultBuffer.add(it.next());
> if (resultBuffer.size() == 1000) {
> JavaRDD<String[]> rdd = jsc.parallelize(resultBuffer);
> // rdd.count();
> rddList.add(rdd);
> resultBuffer.clear();
> }
> }
> JavaRDD<String[]> desc = jsc.union(jsc.parallelize(resultBuffer),
> rddList);
> System.out.println(desc.count());
> this code should duplicate the original RDD, but it just returns an empty
> RDD. Please note that if I uncomment the rdd.count, it will return the
> correct result.
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