mapWith, flatMapWith and filterWith

core/src/main/scala/spark/RDD.scala

@@ -364,6 +364,62 @@ abstract class RDD[T: ClassManifest](
     preservesPartitioning: Boolean = false): RDD[U] =
     new MapPartitionsWithIndexRDD(this, sc.clean(f), preservesPartitioning)
 
+  /**
+   * Maps f over this RDD, where f takes an additional parameter of type A.  This
+   * additional parameter is produced by constructA, which is called in each
+   * partition with the index of that partition.
+   */
+  def mapWith[A: ClassManifest, U: ClassManifest](constructA: Int => A, preservesPartitioning: Boolean = false)
+    (f:(T, A) => U): RDD[U] = {
+      def iterF(index: Int, iter: Iterator[T]): Iterator[U] = {
+        val a = constructA(index)
+        iter.map(t => f(t, a))
+      }
+    new MapPartitionsWithIndexRDD(this, sc.clean(iterF _), preservesPartitioning)
+  }
+
+  /**
+   * FlatMaps f over this RDD, where f takes an additional parameter of type A.  This
+   * additional parameter is produced by constructA, which is called in each
+   * partition with the index of that partition.
+   */
+  def flatMapWith[A: ClassManifest, U: ClassManifest](constructA: Int => A, preservesPartitioning: Boolean = false)
+    (f:(T, A) => Seq[U]): RDD[U] = {
+      def iterF(index: Int, iter: Iterator[T]): Iterator[U] = {
+        val a = constructA(index)
+        iter.flatMap(t => f(t, a))
+      }
+    new MapPartitionsWithIndexRDD(this, sc.clean(iterF _), preservesPartitioning)
+  }
+
+  /**
+   * Applies f to each element of this RDD, where f takes an additional parameter of type A.
+   * This additional parameter is produced by constructA, which is called in each
+   * partition with the index of that partition.
+   */
+  def foreachWith[A: ClassManifest](constructA: Int => A)
+    (f:(T, A) => Unit) {
+      def iterF(index: Int, iter: Iterator[T]): Iterator[T] = {
+        val a = constructA(index)
+        iter.map(t => {f(t, a); t})
+      }
+    (new MapPartitionsWithIndexRDD(this, sc.clean(iterF _), true)).foreach(_ => {})
+  }
+
+  /**
+   * Filters this RDD with p, where p takes an additional parameter of type A.  This
+   * additional parameter is produced by constructA, which is called in each
+   * partition with the index of that partition.
+   */
+  def filterWith[A: ClassManifest](constructA: Int => A)
+    (p:(T, A) => Boolean): RDD[T] = {
+      def iterF(index: Int, iter: Iterator[T]): Iterator[T] = {
+        val a = constructA(index)
+        iter.filter(t => p(t, a))
+      }
+    new MapPartitionsWithIndexRDD(this, sc.clean(iterF _), true)
+  }
+
   /**
    * Zips this RDD with another one, returning key-value pairs with the first element in each RDD,
    * second element in each RDD, etc. Assumes that the two RDDs have the *same number of
@@ -382,6 +438,14 @@ abstract class RDD[T: ClassManifest](
     sc.runJob(this, (iter: Iterator[T]) => iter.foreach(cleanF))
   }
 
+  /**
+   * Applies a function f to each partition of this RDD.
+   */
+  def foreachPartition(f: Iterator[T] => Unit) {
+    val cleanF = sc.clean(f)
+    sc.runJob(this, (iter: Iterator[T]) => f(iter))
+  }
+
   /**
    * Return an array that contains all of the elements in this RDD.
    */
@@ -404,7 +468,7 @@ abstract class RDD[T: ClassManifest](
 
   /**
    * Return an RDD with the elements from `this` that are not in `other`.
-   * 
+   *
    * Uses `this` partitioner/partition size, because even if `other` is huge, the resulting
    * RDD will be <= us.
    */

core/src/test/scala/spark/RDDSuite.scala

@@ -178,4 +178,64 @@ class RDDSuite extends FunSuite with LocalSparkContext {
     assert(prunedData.size === 1)
     assert(prunedData(0) === 10)
   }
+
+  test("mapWith") {
+    import java.util.Random
+    sc = new SparkContext("local", "test")
+    val ones = sc.makeRDD(Array(1, 1, 1, 1, 1, 1), 2)
+    val randoms = ones.mapWith(
+      (index: Int) => new Random(index + 42))
+      {(t: Int, prng: Random) => prng.nextDouble * t}.collect()
+    val prn42_3 = {
+      val prng42 = new Random(42)
+      prng42.nextDouble(); prng42.nextDouble(); prng42.nextDouble()
+    }
+    val prn43_3 = {
+      val prng43 = new Random(43)
+      prng43.nextDouble(); prng43.nextDouble(); prng43.nextDouble()
+    }
+    assert(randoms(2) === prn42_3)
+    assert(randoms(5) === prn43_3)
+  }
+
+  test("flatMapWith") {
+    import java.util.Random
+    sc = new SparkContext("local", "test")
+    val ones = sc.makeRDD(Array(1, 1, 1, 1, 1, 1), 2)
+    val randoms = ones.flatMapWith(
+      (index: Int) => new Random(index + 42))
+      {(t: Int, prng: Random) =>
+        val random = prng.nextDouble()
+        Seq(random * t, random * t * 10)}.
+      collect()
+    val prn42_3 = {
+      val prng42 = new Random(42)
+      prng42.nextDouble(); prng42.nextDouble(); prng42.nextDouble()
+    }
+    val prn43_3 = {
+      val prng43 = new Random(43)
+      prng43.nextDouble(); prng43.nextDouble(); prng43.nextDouble()
+    }
+    assert(randoms(5) === prn42_3 * 10)
+    assert(randoms(11) === prn43_3 * 10)
+  }
+
+  test("filterWith") {
+    import java.util.Random
+    sc = new SparkContext("local", "test")
+    val ints = sc.makeRDD(Array(1, 2, 3, 4, 5, 6), 2)
+    val sample = ints.filterWith(
+      (index: Int) => new Random(index + 42))
+      {(t: Int, prng: Random) => prng.nextInt(3) == 0}.
+      collect()
+    val checkSample = {
+      val prng42 = new Random(42)
+      val prng43 = new Random(43)
+      Array(1, 2, 3, 4, 5, 6).filter{i =>
+	      if (i < 4) 0 == prng42.nextInt(3)
+	      else 0 == prng43.nextInt(3)}
+    }
+    assert(sample.size === checkSample.size)
+    for (i <- 0 until sample.size) assert(sample(i) === checkSample(i))
+  }
 }