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

[Shang Yuanchun (Jira)]

    [ https://issues.apache.org/jira/browse/FLINK-958?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14037895#comment-14037895 ]

Fabian Hueske edited comment on FLINK-958 at 6/19/14 9:12 PM:
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I haven't looked at this issue in detail, but one quick comment.
Sorting the elements of groups on the same key as their grouping key does not make sense ;-)
Within a group the grouping key is always the same, so sorting the elements of a group on the grouping key does not change anything.

Anyways, this does of course not invalidate this issue.
We should
- give a meaningful error message if a user tries to sort groups on their grouping key.
- check if the problem occurs because the sort key is the same as the grouping key
- fix the issue if that is not the case


was (Author: fhueske):
I haven't looked at this issue in detail, but one quick comment.
Sorting a the elements of groups on the same key as their grouping key does not make sense ;-)
Within a group the grouping key is always the same, so sorting the elements of a group on the grouping key does not change anything.

Anyways, this does of course not invalidate this issue.
We should
- give a meaningful error message if a user tries to sort groups on their grouping key.
- check if the problem occurs because the sort key is the same as the grouping key
- fix the issue if that is not the case

> 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}
> Grouping<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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