[HADOOP-5850] map/reduce doesn't run jobs with 0 maps

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 0.20.0
• Fix Version/s: 0.20.1
• Hadoop Flags: Reviewed
• Assignee: Vinod Kumar Vavilapalli
• Reporter: Owen O'Malley
• Created: 15/May/09 16:59
• Updated: 08/Jul/09 16:53
• Resolved: 22/May/09 15:29

Description

Currently, the framework ignores jobs that have 0 maps. This is incorrect. Many pipelines need the job to run (if nothing else, to create the output directory!) so that subsequent jobs don't fail. Effectively, there will be no map tasks and the reduce tasks should immediately set up the Reducer and RecordWriter and then call close on both since there are no inputs to the reduce. I believe it should just work if we remove the check...