[jira] [Commented] (FLINK-2184) Cannot get last element with maxBy/minBy

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-2184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15573301#comment-15573301 ] 

ASF GitHub Bot commented on FLINK-2184:
---------------------------------------

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

    https://github.com/apache/flink/pull/1975#discussion_r83319036
  
    --- Diff: flink-streaming-scala/src/main/scala/org/apache/flink/streaming/api/scala/WindowedStream.scala ---
    @@ -362,38 +362,84 @@ class WindowedStream[T, K, W <: Window](javaStream: JavaWStream[T, K, W]) {
     
       /**
        * Applies an aggregation that that gives the maximum element of the window by
    -   * the given position. When equality, returns the first.
    +   * the given position. When equality, returns the first by default.
        */
       def maxBy(position: Int): DataStream[T] = aggregate(AggregationType.MAXBY,
    -    position)
    +    position, true)
     
       /**
        * Applies an aggregation that that gives the maximum element of the window by
    -   * the given field. When equality, returns the first.
    +   * the given position. When equality, returns either the first or last one depending
    +   * on the parameter setting.
    +   */
    +  def maxBy(position: Int, first: Boolean): DataStream[T] = aggregate(AggregationType.MAXBY,
    +    position, first)
    +
    +  /**
    +   * Applies an aggregation that that gives the maximum element of the window by
    +   * the given field. When equality, returns the first by default.
        */
       def maxBy(field: String): DataStream[T] = aggregate(AggregationType.MAXBY,
    -    field)
    +    field, true)
    +
    +  /**
    +   * Applies an aggregation that that gives the maximum element of the window by
    +   * the given field. When equality, returns either the first or last one depending
    +   * on the parameter setting.
    +   */
    +  def maxBy(field: String, first: Boolean): DataStream[T] = aggregate(AggregationType.MAXBY,
    +    field, first)
     
       /**
        * Applies an aggregation that that gives the minimum element of the window by
    -   * the given position. When equality, returns the first.
    +   * the given position. When equality, returns the first by default.
        */
       def minBy(position: Int): DataStream[T] = aggregate(AggregationType.MINBY,
    -    position)
    +    position, true)
     
       /**
        * Applies an aggregation that that gives the minimum element of the window by
    -   * the given field. When equality, returns the first.
    +   * the given position. When equality, returns either the first or last one depending
    +   * on the parameter setting.
    +   */
    +  def minBy(position: Int, first: Boolean): DataStream[T] = aggregate(AggregationType.MINBY,
    +    position, first)
    +
    +  /**
    +   * Applies an aggregation that that gives the minimum element of the window by
    +   * the given field. When equality, returns the first by default.
        */
       def minBy(field: String): DataStream[T] = aggregate(AggregationType.MINBY,
    -    field)
    +    field, true)
    +
    +  /**
    +   * Applies an aggregation that that gives the minimum element of the window by
    +   * the given field. When equality, returns either the first or last one depending
    +   * on the parameter setting.
    +   */
    +  def minBy(field: String, first: Boolean): DataStream[T] = aggregate(AggregationType.MINBY,
    +    field, first)
    +
    +  private def aggregate(aggregationType: AggregationType, position: Int): DataStream[T] = {
    +    aggregate(aggregationType, position, false)
    +  }
     
       private def aggregate(aggregationType: AggregationType, field: String): DataStream[T] = {
    +    aggregate(aggregationType, field, false)
    --- End diff --
    
    default should be `true` instead of `false`


> Cannot get last element with maxBy/minBy
> ----------------------------------------
>
>                 Key: FLINK-2184
>                 URL: https://issues.apache.org/jira/browse/FLINK-2184
>             Project: Flink
>          Issue Type: Improvement
>          Components: Scala API, Streaming
>            Reporter: Gábor Hermann
>            Priority: Minor
>
> In the streaming Scala API there is no method
> {{maxBy(int positionToMaxBy, boolean first)}}
> nor
> {{minBy(int positionToMinBy, boolean first)}}
> like in the Java API, where _first_ set to {{true}} indicates that the latest found element will return.
> These methods should be added to the Scala API too, in order to be consistent.



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