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From "Andrew Palumbo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (FLINK-3605) DataSet.output(HadoopOutput) always expects a LongWritable as a key and throws an exception when supplied with other Writable Key Types
Date Fri, 11 Mar 2016 02:50:40 GMT
Andrew Palumbo created FLINK-3605:
-------------------------------------

             Summary: DataSet.output(HadoopOutput) always expects a LongWritable as a key
and throws an exception when supplied with other Writable Key Types
                 Key: FLINK-3605
                 URL: https://issues.apache.org/jira/browse/FLINK-3605
             Project: Flink
          Issue Type: Bug
          Components: DataSet API, Scala API
    Affects Versions: 1.0.0
            Reporter: Andrew Palumbo


When trying to output a {{DataSet}} as a Sequence file, using the Scala API, an Exception
it thrown when anything other than a {{LongWritable}} is supplied as a key.  The following
simple unit test demonstrates this:

{code}
  test("Simple DataSet with IntWritable Key and Value") {
    val path = TmpDir + "flinkOutput" 

    implicit val typeInfo = createTypeInformation[(Int,Int)]
    val ds = env.fromElements[(Int, Int)]((1,2), (3,4), (5,6), (7,8))

    val writableDataset : DataSet[(IntWritable, IntWritable)] =
      ds.map( tuple =>
        (new IntWritable(tuple._1.asInstanceOf[Int]), new IntWritable(tuple._2.asInstanceOf[Int]))
    )

    val job: Job = new Job()

    // setup sink for IntWritable
    val sequenceFormat = new SequenceFileOutputFormat[IntWritable,  IntWritable]
    val hadoopOutput  = new HadoopOutputFormat[IntWritable, IntWritable](sequenceFormat, job)
    FileOutputFormat.setOutputPath(job, new org.apache.hadoop.fs.Path(path))

    writableDataset.output(hadoopOutput)

    env.execute(s"dfsWrite($path)")
}
{code}

The above code will throw the following exception:
{code}

{...}
1 [DataSink (org.apache.flink.api.scala.hadoop.mapreduce.HadoopOutputFormat@4d518b32) (1/1)]
ERROR org.apache.flink.runtime.operators.DataSinkTask  - Error in user code: wrong key class:
org.apache.hadoop.io.IntWritable is not class org.apache.hadoop.io.LongWritable:  DataSink
(org.apache.flink.api.scala.hadoop.mapreduce.HadoopOutputFormat@4d518b32) (1/1)
java.io.IOException: wrong key class: org.apache.hadoop.io.IntWritable is not class org.apache.hadoop.io.LongWritable
	at org.apache.hadoop.io.SequenceFile$Writer.append(SequenceFile.java:1305)
	at org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat$1.write(SequenceFileOutputFormat.java:83)
	at org.apache.flink.api.scala.hadoop.mapreduce.HadoopOutputFormat.writeRecord(HadoopOutputFormat.scala:30)
	at org.apache.flink.api.scala.hadoop.mapreduce.HadoopOutputFormat.writeRecord(HadoopOutputFormat.scala:26)
	at org.apache.flink.runtime.operators.DataSinkTask.invoke(DataSinkTask.java:200)
	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:559)
	at java.lang.Thread.run(Thread.java:745)
{code}

When trying to write a {{DataSet}} to a Hadoop Sequence File, the API seems to always expect
a Key of type {{LongWritable}} and a Value of Type {{Text}}.  Similar exceptions are thrown
when other {{Writables}} are used as keys.



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