karanmehta93 commented on issue #419: PHOENIX-4009 Run UPDATE STATISTICS 
command by using MR integration on…
URL: https://github.com/apache/phoenix/pull/419#issuecomment-452927962
 
 
   > this is a common case - we always have some jobs failing after they finish 
most of work (updated > 90% regions) but fail due to some reason, the retry job 
should just do minimal work instead of update stats of the whole table again.
   
   This should not be common case. Common case should be that few mappers can 
fail due to some reason. We have retries for that. The job should NOT fail as a 
whole. Even MR framework doesn't persist data between jobs and can get really 
tricky depending on use cases. Better way is to make the job idempotent so that 
re-run doesn't affect it. 
   
   Also it is hard in this case since we don't know what changed between 
retries. If snapshot name changed, that can potentially affect region 
boundaries. We would need another level of orchestration that persists stats MR 
job information in some table and we look it up before running the current job. 
These cases would be difficult to handle. I would prefer that we try to avoid 
that complexity here.

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