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  1. Flink
  2. FLINK-9221

Add method SinkFunction[A]#contramap[B](f: B => A): SinkFunction[B]

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      Just like it is very useful to use `DataStream[T]` as a sort of Functor or Monad with `map`/`flatMap`/`filter` methods, it would be extremely handy to have a `SinkFunction[A]#contramap[B](f: B => A): SinkFunction[B]` on `SinkFunctions`, so that you can reuse existing complex sink functions, but with a different input type. For example:

      val bucketingStringSink: SinkFunction[String] = 
        new BucketingSink[String]("...")
          .setBucketer(new DateTimeBucketer("yyyy-MM-dd-HHmm")
      
      val bucketingIntListSink: SinkFunction[List[Int]] =
        bucketingStringSink.contramap[List[Int]](_.mkString(","))
      

      For some more formal motivation behind this, https://typelevel.org/cats/typeclasses/contravariant.html is definitely a great place to start!

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            • Assignee:
              yanghua vinoyang
              Reporter:
              joshlemer Josh Lemer
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