Mark Fuhs created MAPREDUCE-4782:
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Summary: 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, 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
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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