[GitHub] [spark] srowen commented on issue #24124: mapPartition to replace map to speedUp Dataset's toLocalIterator process

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srowen commented on issue #24124: mapPartition to replace map to speedUp Dataset's toLocalIterator process
URL: https://github.com/apache/spark/pull/24124#issuecomment-474534742
 
 
   Please fix the title.
   But, why does this improve speed? you're just doing the decoding on the executor vs driver side, without more parallelism. I'm not sure we can/should move the UnsafeRow from executor to driver; may be OK but I'd be wary of changing the semantics here.

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