Prasanth Jayachandran created HIVE-11173:
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             Summary: Fair ordering of fragments in wait queue
                 Key: HIVE-11173
                 URL: https://issues.apache.org/jira/browse/HIVE-11173
             Project: Hive
          Issue Type: Sub-task
    Affects Versions: llap
            Reporter: Prasanth Jayachandran
            Assignee: Prasanth Jayachandran


Wait queue ordering is currently based on the following
1) Finishable or not
2) Vertex parallelism
3) Attempt start time

This ordering has issues in cases when 2 or more queries are execute in 
parallel, then all map tasks gets scheduled first even though reduce task of 
some dag are in finishable state. This will make the first submitted query 
slower even though it can proceed to completion.

Add fair ordering to wait queue comparator to take dag submission time into 
account. For the above scenario, if we take dag submission time into account, 
the first submitted task will proceed to completion.



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