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 0804cdeb048a3..a4905dd51b940 100644 --- a/core/src/main/scala/org/apache/spark/rdd/RDD.scala +++ b/core/src/main/scala/org/apache/spark/rdd/RDD.scala @@ -714,7 +714,13 @@ abstract class RDD[T: ClassTag]( } /** - * Return an RDD created by piping elements to a forked external process. + * Return an RDD created by piping elements to a forked external process. The resulting RDD + * is computed by executing the given process once per partition. All elements + * of each input partition are written to a process's stdin as lines of input separated + * by a newline. The resulting partition consists of the process's stdout output, with + * each line of stdout resulting in one element of the output partition. A process is invoked + * even for empty partitions. + * * The print behavior can be customized by providing two functions. * * @param command command to run in forked process. diff --git a/core/src/test/scala/org/apache/spark/rdd/PipedRDDSuite.scala b/core/src/test/scala/org/apache/spark/rdd/PipedRDDSuite.scala index 5d56fc19f00e1..f8d523fa2c6ae 100644 --- a/core/src/test/scala/org/apache/spark/rdd/PipedRDDSuite.scala +++ b/core/src/test/scala/org/apache/spark/rdd/PipedRDDSuite.scala @@ -138,6 +138,14 @@ class PipedRDDSuite extends SparkFunSuite with SharedSparkContext { } } + test("pipe with empty partition") { + val data = sc.parallelize(Seq("foo", "bing"), 8) + val piped = data.pipe("wc -c") + assert(piped.count == 8) + val charCounts = piped.map(_.trim.toInt).collect().toSet + assert(Set(0, 4, 5) == charCounts) + } + test("pipe with env variable") { if (testCommandAvailable("printenv")) { val nums = sc.makeRDD(Array(1, 2, 3, 4), 2)