[MAPREDUCE-4782] NLineInputFormat skips first line of last InputSplit

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.22.0, 0.23.0, 1.0.0, 2.0.0-alpha
• Fix Version/s: 1.1.1, 2.0.3-alpha, 0.23.5
• Component/s: client

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");

• Target Version/s: 1.1.1, 0.23.5
• Assignee: Mark Fuhs
• Reporter: Mark Fuhs
• Created: 08/Nov/12 19:54
• Updated: 10/Mar/15 04:30
• Resolved: 09/Nov/12 16:03

Description

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.