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From scwf <...@git.apache.org>
Subject [GitHub] spark issue #16633: [SPARK-19274][SQL] Make GlobalLimit without shuffling da...
Date Fri, 20 Jan 2017 03:08:28 GMT
Github user scwf commented on the issue:

    https://github.com/apache/spark/pull/16633
  
    For 1,  my idea is not use the proposal in this PR, 
    1. how you determine  `total rows in all partitions are (much) more than limit number.`
and then go into this code path and how to decide the `much more than`,  i can not use cbo
estimate stats here because the locallimit plan maybe complex and we can not ensure the accuracy
of the estimate row number.  
    2 as @rxin suggest, this break the rdd chain
    
    So for 1, i think it need some improvement of spark core and scheduler as i mentioned
above
    
    For 2 it is ok to me, the solution is the same with i described above(still shuffle +shuffle
to multi partition + modified mapoutput statistics), right?


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