[jira] [Created] (FLINK-958) Sorting a group when key is a Writable gives a NonSerializable Error

[Artem Tsikiridis (JIRA)]

Artem Tsikiridis created FLINK-958:
--------------------------------------

             Summary: Sorting a group when key is a Writable gives a 
NonSerializable Error
                 Key: FLINK-958
                 URL: https://issues.apache.org/jira/browse/FLINK-958
             Project: Flink
          Issue Type: Bug
          Components: Java API
            Reporter: Artem Tsikiridis


I cannot sort an unsorted group by key when the key Is a Writable. Is it a bug?

Consider:
{code}
DataSet<Tuple2<Text, LongWritable>> res = myData
                                .map(new MapFunction<Tuple2<String, Long>, 
Tuple2<Text, LongWritable>>() {

                                        @Override
                                        public Tuple2<Text, LongWritable> map(
                                                        Tuple2<String, Long> 
value) throws Exception {
                                                return new Tuple2<Text, 
LongWritable>(new Text(value.f0), new LongWritable(value.f1));
                                        }
                                })
                                .groupBy(0).sortGroup(0, Order.ASCENDING)
{code}

This gives the following stacktrace:

{code}
Caused by: java.io.NotSerializableException: sun.misc.Launcher$AppClassLoader
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1183)
        at 
java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1547)
        at 
java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1508)
        at 
java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1431)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1177)
        at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1377)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1173)
        at 
java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1547)
        at 
java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1508)
        at 
java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1431)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1177)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
        at 
eu.stratosphere.util.InstantiationUtil.serializeObject(InstantiationUtil.java:250)
        at 
eu.stratosphere.util.InstantiationUtil.writeObjectToConfig(InstantiationUtil.java:231)
        at 
eu.stratosphere.api.java.typeutils.runtime.RuntimeComparatorFactory.writeParametersToConfig(RuntimeComparatorFactory.java:40)
        ... 14 more
{code}

Is it not supported to sort groupings with writables as keys? I understand this 
is a hadoop serialization error, but so far I am not able to fix it.

Any ideas?



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