[GitHub] spark pull request #19621: [SPARK-11215][ML] Add multiple columns support to...

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

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

    https://github.com/apache/spark/pull/19621#discussion_r148172976
  
    --- Diff: mllib/src/main/scala/org/apache/spark/ml/feature/StringIndexer.scala ---
    @@ -130,21 +152,33 @@ class StringIndexer @Since("1.4.0") (
       @Since("1.4.0")
       def setOutputCol(value: String): this.type = set(outputCol, value)
     
    +  /** @group setParam */
    +  @Since("2.3.0")
    +  def setInputCols(value: Array[String]): this.type = set(inputCols, value)
    +
    +  /** @group setParam */
    +  @Since("2.3.0")
    +  def setOutputCols(value: Array[String]): this.type = set(outputCols, value)
    +
       @Since("2.0.0")
       override def fit(dataset: Dataset[_]): StringIndexerModel = {
         transformSchema(dataset.schema, logging = true)
    -    val values = dataset.na.drop(Array($(inputCol)))
    -      .select(col($(inputCol)).cast(StringType))
    -      .rdd.map(_.getString(0))
    -    val labels = $(stringOrderType) match {
    -      case StringIndexer.frequencyDesc => values.countByValue().toSeq.sortBy(-_._2)
    -        .map(_._1).toArray
    -      case StringIndexer.frequencyAsc => values.countByValue().toSeq.sortBy(_._2)
    -        .map(_._1).toArray
    -      case StringIndexer.alphabetDesc => values.distinct.collect.sortWith(_ > _)
    -      case StringIndexer.alphabetAsc => values.distinct.collect.sortWith(_ < _)
    +
    +    val labelsArray = for (inputCol <- getInOutCols._1) yield {
    +      val values = dataset.na.drop(Array(inputCol))
    +        .select(col(inputCol).cast(StringType))
    +        .rdd.map(_.getString(0))
    --- End diff --
    
    This gets the values for each input column sequentially. Can we get the values for all input columns at one run?


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