[GitHub] spark pull request #17014: [SPARK-18608][ML] Fix double-caching in ML algori...

[hhbyyh <gi...@git.apache.org>]

Github user hhbyyh commented on a diff in the pull request:

    https://github.com/apache/spark/pull/17014#discussion_r107515202
  
    --- Diff: mllib/src/main/scala/org/apache/spark/ml/classification/DecisionTreeClassifier.scala ---
    @@ -110,12 +111,17 @@ class DecisionTreeClassifier @Since("1.4.0") (
         val oldDataset: RDD[LabeledPoint] = extractLabeledPoints(dataset, numClasses)
         val strategy = getOldStrategy(categoricalFeatures, numClasses)
     
    -    val instr = Instrumentation.create(this, oldDataset)
    +    val handlePersistence = storageLevel == StorageLevel.NONE
    +    if (handlePersistence) oldDataset.persist(StorageLevel.MEMORY_AND_DISK)
    --- End diff --
    
    `storageLevel == StorageLevel.NONE` could be a function defined in `Predictor` to avoid code duplicates.
    
    I'm not sure if we always want to use `StorageLevel.MEMORY_AND_DISK`, but it will be good to have some flexibility. How about adding a field to represent `StorageLevel.MEMORY_AND_DISK`?


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