SPARK-1063 Add .sortBy(f) method on RDD

This never got merged from the apache/incubator-spark repo (which is now deleted) but there had been several rounds of code review on this PR there.

I think this is ready for merging.

Author: Andrew Ash <andrew@andrewash.com>

This patch had conflicts when merged, resolved by
Committer: Reynold Xin <rxin@apache.org>

Closes #369 from ash211/sortby and squashes the following commits:

d09147a [Andrew Ash] Fix Ordering import
43d0a53 [Andrew Ash] Fix missing .collect()
29a54ed [Andrew Ash] Re-enable test by converting to a closure
5a95348 [Andrew Ash] Add license for RDDSuiteUtils
64ed6e3 [Andrew Ash] Remove leaked diff
d4de69a [Andrew Ash] Remove scar tissue
63638b5 [Andrew Ash] Add Python version of .sortBy()
45e0fde [Andrew Ash] Add Java version of .sortBy()
adf84c5 [Andrew Ash] Re-indent to keep line lengths under 100 chars
9d9b9d8 [Andrew Ash] Use parentheses on .collect() calls
0457b69 [Andrew Ash] Ignore failing test
99f0baf [Andrew Ash] Merge branch 'master' into sortby
222ae97 [Andrew Ash] Try moving Ordering objects out to a different class
3fd0dd3 [Andrew Ash] Add (failing) test for sortByKey with explicit Ordering
b8b5bbc [Andrew Ash] Align remove extra spaces that were used to align ='s in test code
8c53298 [Andrew Ash] Actually use ascending and numPartitions parameters
381eef2 [Andrew Ash] Correct silly typo
7db3e84 [Andrew Ash] Support ascending and numPartitions params in sortBy()
0f685fd [Andrew Ash] Merge remote-tracking branch 'origin/master' into sortby
ca4490d [Andrew Ash] Add .sortBy(f) method on RDD

6 files changed, 159 insertions, 4 deletions

diff --git a/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala b/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
index 23d1371079..86fb374bef 100644
--- a/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
+++ b/core/src/main/scala/org/apache/spark/api/java/JavaRDD.scala
@@ -17,10 +17,13 @@
 
 package org.apache.spark.api.java
 
+import java.util.Comparator
+
 import scala.language.implicitConversions
 import scala.reflect.ClassTag
 
 import org.apache.spark._
+import org.apache.spark.api.java.JavaSparkContext.fakeClassTag
 import org.apache.spark.api.java.function.{Function => JFunction}
 import org.apache.spark.rdd.RDD
 import org.apache.spark.storage.StorageLevel
@@ -172,6 +175,19 @@ class JavaRDD[T](val rdd: RDD[T])(implicit val classTag: ClassTag[T])
     rdd.setName(name)
     this
   }
+
+  /**
+   * Return this RDD sorted by the given key function.
+   */
+  def sortBy[S](f: JFunction[T, S], ascending: Boolean, numPartitions: Int): JavaRDD[T] = {
+    import scala.collection.JavaConverters._
+    def fn = (x: T) => f.call(x)
+    import com.google.common.collect.Ordering  // shadows scala.math.Ordering
+    implicit val ordering = Ordering.natural().asInstanceOf[Ordering[S]]
+    implicit val ctag: ClassTag[S] = fakeClassTag
+    wrapRDD(rdd.sortBy(fn, ascending, numPartitions))
+  }
+
 }
 
 object JavaRDD {
diff --git a/core/src/main/scala/org/apache/spark/rdd/RDD.scala b/core/src/main/scala/org/apache/spark/rdd/RDD.scala
index 27cc60d775..cf915b870e 100644
--- a/core/src/main/scala/org/apache/spark/rdd/RDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/RDD.scala
@@ -443,6 +443,18 @@ abstract class RDD[T: ClassTag](
   def ++(other: RDD[T]): RDD[T] = this.union(other)
 
   /**
+   * Return this RDD sorted by the given key function.
+   */
+  def sortBy[K](
+      f: (T) ⇒ K,
+      ascending: Boolean = true,
+      numPartitions: Int = this.partitions.size)
+      (implicit ord: Ordering[K], ctag: ClassTag[K]): RDD[T] =
+    this.keyBy[K](f)
+        .sortByKey(ascending, numPartitions)
+        .values
+
+  /**
    * Return the intersection of this RDD and another one. The output will not contain any duplicate
    * elements, even if the input RDDs did.
    *
diff --git a/core/src/test/java/org/apache/spark/JavaAPISuite.java b/core/src/test/java/org/apache/spark/JavaAPISuite.java
index ef41bfb88d..e46298c6a9 100644
--- a/core/src/test/java/org/apache/spark/JavaAPISuite.java
+++ b/core/src/test/java/org/apache/spark/JavaAPISuite.java
@@ -181,6 +181,39 @@ public class JavaAPISuite implements Serializable {
   }
 
   @Test
+  public void sortBy() {
+    List<Tuple2<Integer, Integer>> pairs = new ArrayList<Tuple2<Integer, Integer>>();
+    pairs.add(new Tuple2<Integer, Integer>(0, 4));
+    pairs.add(new Tuple2<Integer, Integer>(3, 2));
+    pairs.add(new Tuple2<Integer, Integer>(-1, 1));
+
+    JavaRDD<Tuple2<Integer, Integer>> rdd = sc.parallelize(pairs);
+
+    // compare on first value
+    JavaRDD<Tuple2<Integer, Integer>> sortedRDD = rdd.sortBy(new Function<Tuple2<Integer, Integer>, Integer>() {
+      public Integer call(Tuple2<Integer, Integer> t) throws Exception {
+        return t._1();
+      }
+    }, true, 2);
+
+    Assert.assertEquals(new Tuple2<Integer, Integer>(-1, 1), sortedRDD.first());
+    List<Tuple2<Integer, Integer>> sortedPairs = sortedRDD.collect();
+    Assert.assertEquals(new Tuple2<Integer, Integer>(0, 4), sortedPairs.get(1));
+    Assert.assertEquals(new Tuple2<Integer, Integer>(3, 2), sortedPairs.get(2));
+
+    // compare on second value
+    sortedRDD = rdd.sortBy(new Function<Tuple2<Integer, Integer>, Integer>() {
+      public Integer call(Tuple2<Integer, Integer> t) throws Exception {
+        return t._2();
+      }
+    }, true, 2);
+    Assert.assertEquals(new Tuple2<Integer, Integer>(-1, 1), sortedRDD.first());
+    sortedPairs = sortedRDD.collect();
+    Assert.assertEquals(new Tuple2<Integer, Integer>(3, 2), sortedPairs.get(1));
+    Assert.assertEquals(new Tuple2<Integer, Integer>(0, 4), sortedPairs.get(2));
+  }
+
+  @Test
   public void foreach() {
     final Accumulator<Integer> accum = sc.accumulator(0);
     JavaRDD<String> rdd = sc.parallelize(Arrays.asList("Hello", "World"));
diff --git a/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala b/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
index e94a1e76d4..0e5625b764 100644
--- a/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
+++ b/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
@@ -26,6 +26,8 @@ import org.apache.spark._
 import org.apache.spark.SparkContext._
 import org.apache.spark.util.Utils
 
+import org.apache.spark.rdd.RDDSuiteUtils._
+
 class RDDSuite extends FunSuite with SharedSparkContext {
 
   test("basic operations") {
@@ -585,14 +587,63 @@ class RDDSuite extends FunSuite with SharedSparkContext {
     }
   }
 
+  test("sortByKey") {
+    val data = sc.parallelize(Seq("5|50|A","4|60|C", "6|40|B"))
+
+    val col1 = Array("4|60|C", "5|50|A", "6|40|B")
+    val col2 = Array("6|40|B", "5|50|A", "4|60|C")
+    val col3 = Array("5|50|A", "6|40|B", "4|60|C")
+
+    assert(data.sortBy(_.split("\\|")(0)).collect() === col1)
+    assert(data.sortBy(_.split("\\|")(1)).collect() === col2)
+    assert(data.sortBy(_.split("\\|")(2)).collect() === col3)
+  }
+
+  test("sortByKey ascending parameter") {
+    val data = sc.parallelize(Seq("5|50|A","4|60|C", "6|40|B"))
+
+    val asc = Array("4|60|C", "5|50|A", "6|40|B")
+    val desc = Array("6|40|B", "5|50|A", "4|60|C")
+
+    assert(data.sortBy(_.split("\\|")(0), true).collect() === asc)
+    assert(data.sortBy(_.split("\\|")(0), false).collect() === desc)
+  }
+
+  test("sortByKey with explicit ordering") {
+    val data = sc.parallelize(Seq("Bob|Smith|50",
+                                  "Jane|Smith|40",
+                                  "Thomas|Williams|30",
+                                  "Karen|Williams|60"))
+
+    val ageOrdered = Array("Thomas|Williams|30",
+                           "Jane|Smith|40",
+                           "Bob|Smith|50",
+                           "Karen|Williams|60")
+
+    // last name, then first name
+    val nameOrdered = Array("Bob|Smith|50",
+                            "Jane|Smith|40",
+                            "Karen|Williams|60",
+                            "Thomas|Williams|30")
+
+    val parse = (s: String) => {
+      val split = s.split("\\|")
+      Person(split(0), split(1), split(2).toInt)
+    }
+
+    import scala.reflect.classTag
+    assert(data.sortBy(parse, true, 2)(AgeOrdering, classTag[Person]).collect() === ageOrdered)
+    assert(data.sortBy(parse, true, 2)(NameOrdering, classTag[Person]).collect() === nameOrdered)
+  }
+
   test("intersection") {
     val all = sc.parallelize(1 to 10)
     val evens = sc.parallelize(2 to 10 by 2)
     val intersection = Array(2, 4, 6, 8, 10)
 
     // intersection is commutative
-    assert(all.intersection(evens).collect.sorted === intersection)
-    assert(evens.intersection(all).collect.sorted === intersection)
+    assert(all.intersection(evens).collect().sorted === intersection)
+    assert(evens.intersection(all).collect().sorted === intersection)
   }
 
   test("intersection strips duplicates in an input") {
@@ -600,8 +651,8 @@ class RDDSuite extends FunSuite with SharedSparkContext {
     val b = sc.parallelize(Seq(1,1,2,3))
     val intersection = Array(1,2,3)
 
-    assert(a.intersection(b).collect.sorted === intersection)
-    assert(b.intersection(a).collect.sorted === intersection)
+    assert(a.intersection(b).collect().sorted === intersection)
+    assert(b.intersection(a).collect().sorted === intersection)
   }
 
   test("zipWithIndex") {
diff --git a/core/src/test/scala/org/apache/spark/rdd/RDDSuiteUtils.scala b/core/src/test/scala/org/apache/spark/rdd/RDDSuiteUtils.scala
new file mode 100644
index 0000000000..4762fc1785
--- /dev/null
+++ b/core/src/test/scala/org/apache/spark/rdd/RDDSuiteUtils.scala
@@ -0,0 +1,31 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.rdd
+
+object RDDSuiteUtils {
+  case class Person(first: String, last: String, age: Int)
+
+  object AgeOrdering extends Ordering[Person] {
+    def compare(a:Person, b:Person) = a.age compare b.age
+  }
+
+  object NameOrdering extends Ordering[Person] {
+    def compare(a:Person, b:Person) =
+      implicitly[Ordering[Tuple2[String,String]]].compare((a.last, a.first), (b.last, b.first))
+  }
+}
diff --git a/python/pyspark/rdd.py b/python/pyspark/rdd.py
index bb4d035edc..65f63153cd 100644
--- a/python/pyspark/rdd.py
+++ b/python/pyspark/rdd.py
@@ -549,6 +549,18 @@ class RDD(object):
                     .mapPartitions(mapFunc,preservesPartitioning=True)
                     .flatMap(lambda x: x, preservesPartitioning=True))
 
+    def sortBy(self, keyfunc, ascending=True, numPartitions=None):
+        """
+        Sorts this RDD by the given keyfunc
+
+        >>> tmp = [('a', 1), ('b', 2), ('1', 3), ('d', 4), ('2', 5)]
+        >>> sc.parallelize(tmp).sortBy(lambda x: x[0]).collect()
+        [('1', 3), ('2', 5), ('a', 1), ('b', 2), ('d', 4)]
+        >>> sc.parallelize(tmp).sortBy(lambda x: x[1]).collect()
+        [('a', 1), ('b', 2), ('1', 3), ('d', 4), ('2', 5)]
+        """
+        return self.keyBy(keyfunc).sortByKey(ascending, numPartitions).values()
+
     def glom(self):
         """
         Return an RDD created by coalescing all elements within each partition