The partitionMapper on a restart can choose to override the previous partitioning and start fresh. If it does, when (the spec doesn't say) do we forget about the results of the previous run? What if the job crashes right after the mapper returns but before we do anything? Are there supposed to be previous results or not for the next restart? What do we do on a restart with no previous partition plan if the next try says to pick up where we left off?
The partitionMapper on a restart can choose to override the previous partitioning and start fresh. If it does, when (the spec doesn't say) do we forget about the results of the previous run? What if the job crashes right after the mapper returns but before we do anything? Are there supposed to be previous results or not for the next restart? What do we do on a restart with no previous partition plan if the next try says to pick up where we left off?