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https://issues.apache.org/jira/browse/MAPREDUCE-5530?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13777905#comment-13777905
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Robert Kanter commented on MAPREDUCE-5530:
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Tell me if I'm understanding 2 correctly: If the subclass implements
{{isSplitable(FileSystem fs, Path file)}}, then the user is expecting that it
will actually be used by other methods, such as {{getSplits()}}; except that it
won't be, because they're using {{isSplittable(JobContext context, Path file)}}
instead. So, if the subclass relies on its implementation of {{isSplitale
FileSystem fs, Path file)}}, then it will compile and run, but it won't
logically work correctly.
One idea would be to AND or OR the results of both {{isSplitable}} methods when
calling either one of them, but that would require subclasses to override both
and probably be confusing.
Other than that, I'm not really sure of a good solution either. Perhaps
someone else has an idea?
> Binary and source incompatibility in mapred.lib.CombineFileInputFormat
> between branch-1 and branch-2
> ----------------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-5530
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5530
> Project: Hadoop Map/Reduce
> Issue Type: Sub-task
> Components: mrv1, mrv2
> Affects Versions: 2.1.1-beta
> Reporter: Robert Kanter
> Assignee: Robert Kanter
> Priority: Blocker
> Attachments: MAPREDUCE-5530.patch
>
>
> {{mapred.lib.CombineFileInputFormat}} in branch-1 has this method:
> {code:java}
> protected boolean isSplitable(FileSystem fs, Path file)
> {code}
> In branch-2, {{mapred.lib.CombineFileInputFormat}} is now a subclass of
> {{mapreduce.lib.input.CombineFileInputFormat}}, from which it inherits the
> similar method:
> {code:java}
> protected boolean isSplitable(JobContext context, Path file)
> {code}
> This means that any code that subclasses
> {{mapred.lib.CombineFileInputFormat}} and does not provide its own
> implementation of {{protected boolean isSplitable(FileSystem fs, Path file)}}
> will not be binary or source compatible if it tries to call {{isSplitable}}
> with a {{FileSystem}} argument anywhere (that is, if compiled against
> branch-1, it will throw a {{NoSuchMethodError}} if run against branch-2;
> also, it won't even compile against branch-2).
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