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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-4872) Type erasure problem exclusively on cluster execution
Date Mon, 28 Nov 2016 15:57:58 GMT

    [ https://issues.apache.org/jira/browse/FLINK-4872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15702317#comment-15702317
] 

ASF GitHub Bot commented on FLINK-4872:
---------------------------------------

Github user twalthr commented on the issue:

    https://github.com/apache/flink/pull/2823
  
    Merging...


> Type erasure problem exclusively on cluster execution
> -----------------------------------------------------
>
>                 Key: FLINK-4872
>                 URL: https://issues.apache.org/jira/browse/FLINK-4872
>             Project: Flink
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.1.2
>            Reporter: Martin Junghanns
>            Assignee: Timo Walther
>
> The following codes runs fine on local and collection execution environment but fails
when executed on a cluster.
> {code:title=Problem.java}
> import org.apache.flink.api.common.functions.MapFunction;
> import org.apache.flink.api.java.DataSet;
> import org.apache.flink.api.java.ExecutionEnvironment;
> import org.apache.flink.api.java.tuple.Tuple1;
> import java.lang.reflect.Array;
> public class Problem {
>   public static class Pojo {
>   }
>   public static class Foo<T> extends Tuple1<T> {
>   }
>   public static class Bar<T> extends Tuple1<T[]> {
>   }
>   public static class UDF<T> implements MapFunction<Foo<T>, Bar<T>>
{
>     private final Class<T> clazz;
>     public UDF(Class<T> clazz) {
>       this.clazz = clazz;
>     }
>     @Override
>     public Bar<T> map(Foo<T> value) throws Exception {
>       Bar<T> bar = new Bar<>();
>       //noinspection unchecked
>       bar.f0 = (T[]) Array.newInstance(clazz, 10);
>       return bar;
>     }
>   }
>   public static void main(String[] args) throws Exception {
>     // runs in local, collection and cluster execution
>     withLong();
>     // runs in local and collection execution, fails on cluster execution
>     withPojo();
>   }
>   public static void withLong() throws Exception {
>     ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
>     Foo<Long> foo = new Foo<>();
>     foo.f0 = 42L;
>     DataSet<Foo<Long>> barDataSource = env.fromElements(foo);
>     DataSet<Bar<Long>> map = barDataSource.map(new UDF<>(Long.class));
>     map.print();
>   }
>   public static void withPojo() throws Exception {
>     ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
>     Foo<Pojo> foo = new Foo<>();
>     foo.f0 = new Pojo();
>     DataSet<Foo<Pojo>> barDataSource = env.fromElements(foo);
>     DataSet<Bar<Pojo>> map = barDataSource.map(new UDF<>(Pojo.class));
>     map.print();
>   }
> }
> {code}
> {code:title=ProblemTest.java}
> import org.apache.flink.test.util.MultipleProgramsTestBase;
> import org.junit.Test;
> import org.junit.runner.RunWith;
> import org.junit.runners.Parameterized;
> @RunWith(Parameterized.class)
> public class ProblemTest extends MultipleProgramsTestBase {
>   public ProblemTest(TestExecutionMode mode) {
>     super(mode);
>   }
>   @Test
>   public void testWithLong() throws Exception {
>     Problem.withLong();
>   }
>   @Test
>   public void testWithPOJO() throws Exception {
>     Problem.withPojo();
>   }
> }
> {code}
> Exception:
> {code}
> The return type of function 'withPojo(Problem.java:58)' could not be determined automatically,
due to type erasure. You can give type information hints by using the returns(...) method
on the result of the transformation call, or by letting your function implement the 'ResultTypeQueryable'
interface.
>     org.apache.flink.api.java.DataSet.getType(DataSet.java:178)
>     org.apache.flink.api.java.DataSet.collect(DataSet.java:407)
>     org.apache.flink.api.java.DataSet.print(DataSet.java:1605)
>     Problem.withPojo(Problem.java:60)
>     Problem.main(Problem.java:38) 
> {code}



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