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From "Matt Foley (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-4782) NLineInputFormat skips first line of last InputSplit
Date Tue, 20 Nov 2012 21:36:58 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-4782?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Matt Foley updated MAPREDUCE-4782:
----------------------------------

    Fix Version/s:     (was: 1.2.0)
    
> NLineInputFormat skips first line of last InputSplit
> ----------------------------------------------------
>
>                 Key: MAPREDUCE-4782
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4782
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 0.22.0, 0.23.0, 1.0.0, 2.0.0-alpha, trunk
>         Environment: job.setMapperClass(Mapper.class);  // just pass text lines through
to output
> job.setInputFormatClass(NLineInputFormat.class);
> NLineInputFormat.setNumLinesPerSplit(job, 100);
> NLineInputFormat.setInputPaths(job, "/path/to/a_file_with_many_lines.txt");
>            Reporter: Mark Fuhs
>            Assignee: Mark Fuhs
>            Priority: Blocker
>             Fix For: 1.1.1, 3.0.0, 2.0.3-alpha, 0.23.5
>
>         Attachments: MAPREDUCE-4782.patch, MR-4782-branch-1.txt, MR-4782.txt
>
>
> NLineInputFormat creates FileSplits that are then used by LineRecordReader to generate
Text values. To deal with an idiosyncrasy of LineRecordReader, the begin and length fields
of the FileSplit are constructed differently for the first FileSplit vs. the rest.
> After looping through all lines of a file, the final FileSplit is created, but the creation
does not respect the difference of how the first vs. the rest of the FileSplits are created.
> This results in the first line of the final InputSplit being skipped. I've created a
patch to NLineInputFormat, and this fixes the problem.

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