[SPARK-15512][CORE] repartition(0) should raise IllegalArgumentException

## What changes were proposed in this pull request?

Previously, SPARK-8893 added the constraints on positive number of partitions for repartition/coalesce operations in general. This PR adds one missing part for that and adds explicit two testcases.

**Before**
```scala
scala> sc.parallelize(1 to 5).coalesce(0)
java.lang.IllegalArgumentException: requirement failed: Number of partitions (0) must be positive.
...
scala> sc.parallelize(1 to 5).repartition(0).collect()
res1: Array[Int] = Array()   // empty
scala> spark.sql("select 1").coalesce(0)
res2: org.apache.spark.sql.Dataset[org.apache.spark.sql.Row] = [1: int]
scala> spark.sql("select 1").coalesce(0).collect()
java.lang.IllegalArgumentException: requirement failed: Number of partitions (0) must be positive.
scala> spark.sql("select 1").repartition(0)
res3: org.apache.spark.sql.Dataset[org.apache.spark.sql.Row] = [1: int]
scala> spark.sql("select 1").repartition(0).collect()
res4: Array[org.apache.spark.sql.Row] = Array()  // empty
```

**After**
```scala
scala> sc.parallelize(1 to 5).coalesce(0)
java.lang.IllegalArgumentException: requirement failed: Number of partitions (0) must be positive.
...
scala> sc.parallelize(1 to 5).repartition(0)
java.lang.IllegalArgumentException: requirement failed: Number of partitions (0) must be positive.
...
scala> spark.sql("select 1").coalesce(0)
java.lang.IllegalArgumentException: requirement failed: Number of partitions (0) must be positive.
...
scala> spark.sql("select 1").repartition(0)
java.lang.IllegalArgumentException: requirement failed: Number of partitions (0) must be positive.
...
```

## How was this patch tested?

Pass the Jenkins tests with new testcases.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #13282 from dongjoon-hyun/SPARK-15512.

2 files changed, 9 insertions, 0 deletions

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 e6db9b3eec..e251421c48 100644
--- a/core/src/main/scala/org/apache/spark/rdd/RDD.scala
+++ b/core/src/main/scala/org/apache/spark/rdd/RDD.scala
@@ -437,6 +437,7 @@ abstract class RDD[T: ClassTag](
                partitionCoalescer: Option[PartitionCoalescer] = Option.empty)
               (implicit ord: Ordering[T] = null)
       : RDD[T] = withScope {
+    require(numPartitions > 0, s"Number of partitions ($numPartitions) must be positive.")
     if (shuffle) {
       /** Distributes elements evenly across output partitions, starting from a random partition. */
       val distributePartition = (index: Int, items: Iterator[T]) => {
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 a4992fe8ac..ad56715656 100644
--- a/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
+++ b/core/src/test/scala/org/apache/spark/rdd/RDDSuite.scala
@@ -276,6 +276,10 @@ class RDDSuite extends SparkFunSuite with SharedSparkContext {
   test("repartitioned RDDs") {
     val data = sc.parallelize(1 to 1000, 10)
 
+    intercept[IllegalArgumentException] {
+      data.repartition(0)
+    }
+
     // Coalesce partitions
     val repartitioned1 = data.repartition(2)
     assert(repartitioned1.partitions.size == 2)
@@ -329,6 +333,10 @@ class RDDSuite extends SparkFunSuite with SharedSparkContext {
   test("coalesced RDDs") {
     val data = sc.parallelize(1 to 10, 10)
 
+    intercept[IllegalArgumentException] {
+      data.coalesce(0)
+    }
+
     val coalesced1 = data.coalesce(2)
     assert(coalesced1.collect().toList === (1 to 10).toList)
     assert(coalesced1.glom().collect().map(_.toList).toList ===