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From tdas <...@git.apache.org>
Subject [GitHub] spark pull request: [SPARK-4999][Streaming] Change storeInBlockMan...
Date Tue, 06 Jan 2015 09:24:33 GMT
Github user tdas commented on the pull request:

    https://github.com/apache/spark/pull/3906#issuecomment-68843161
  
    If you are using a window operations, then previous batches data may need to be access
multiple times. If we dont put the data in WAL back in memory, the system will have to read
the data multiple times from the WAL. That's going to be very slow, isnt it.
    
    A smarter thing to do is to figure (based on the transformations) whether the data is
going to required multiple times or not, and accordingly store the data in BM. Just turning
it blindly setting it to false will cause a performance regression.


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