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https://issues.apache.org/jira/browse/FLINK-3166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15061837#comment-15061837
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ASF GitHub Bot commented on FLINK-3166:
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Github user zentol commented on the pull request:
https://github.com/apache/flink/pull/1464#issuecomment-165406987
A few comments:
* the change to the TestEnvironment is unnecessary; ObjectReuse is
enabled/disabled in the JavaProgramTestBase. it doesn't fix anything, removing
the call to enabledObjectReuse in the test already did the trick.
* The ObjectReuseITCase is supposed to verify that objects are reused. Now,
the results are the same regardless of whether they are reused (except in case
3), making it little more then a reduce test. (There is also little point of
running this test with ObjectReuse disabled, which is why it forced it)
* A little bit above your changes in Reduce(Combine)Driver is a comment as
to why we only need 2 objects when reusing objects, this will need to be
adjusted.
* I like the changes in DataSourceTask/Reduce(Combine)Driver. They are a
seemingly simple solution for a common problem. In fact, But i am a bit
apprehensive about them, because i have a hard time imagining that no one else
could think of them; there might be a bigger issue with changes that i can't
see at the moment.
> The first program in ObjectReuseITCase has the wrong expected result, and it
> succeeds
> -------------------------------------------------------------------------------------
>
> Key: FLINK-3166
> URL: https://issues.apache.org/jira/browse/FLINK-3166
> Project: Flink
> Issue Type: Bug
> Components: Distributed Runtime, Documentation, Tests
> Reporter: Gabor Gevay
> Assignee: Greg Hogan
> Priority: Critical
>
> The first program in ObjectReuseITCase has the following input:
> a,1
> a,2
> a,3
> a,4
> a,50
> There is a groupBy on field 0, and then a reduce, so the result should be
> 1+2+3+4+50 = 60. But the hardcoded expected result is 100, and running the
> Flink program also produces this.
> The problem is caused my mismatched assumptions between
> ReduceCombineDriver.sortAndCombine and the ReduceFunction in the test about
> object reuse rules of ReduceFunctions:
> ReduceCombineDriver.sortAndCombine has the following comment:
> "The user function is expected to return the first input as the result."
> While the ReduceFunction in the test is modifying and returning the second
> input. (And the second program in the test also has the same problem.)
> I can't find the assumption that is stated in the comment in any
> documentation. For example, the javadoc of ReduceFunction should make the
> user aware of this. Or, alternatively, the code of the driver should be
> modified to not make this assumption. I'm not sure which solution is better.
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