diff options
| -rw-r--r-- | core/src/main/scala/org/apache/spark/SparkContext.scala | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/core/src/main/scala/org/apache/spark/SparkContext.scala b/core/src/main/scala/org/apache/spark/SparkContext.scala index 8fbda2c667..35970c2f50 100644 --- a/core/src/main/scala/org/apache/spark/SparkContext.scala +++ b/core/src/main/scala/org/apache/spark/SparkContext.scala @@ -434,12 +434,21 @@ class SparkContext(config: SparkConf) extends Logging { // Methods for creating RDDs - /** Distribute a local Scala collection to form an RDD. */ + /** Distribute a local Scala collection to form an RDD. + * + * @note Parallelize acts lazily. If `seq` is a mutable collection and is + * altered after the call to parallelize and before the first action on the + * RDD, the resultant RDD will reflect the modified collection. Pass a copy of + * the argument to avoid this. + */ def parallelize[T: ClassTag](seq: Seq[T], numSlices: Int = defaultParallelism): RDD[T] = { new ParallelCollectionRDD[T](this, seq, numSlices, Map[Int, Seq[String]]()) } - /** Distribute a local Scala collection to form an RDD. */ + /** Distribute a local Scala collection to form an RDD. + * + * This method is identical to `parallelize`. + */ def makeRDD[T: ClassTag](seq: Seq[T], numSlices: Int = defaultParallelism): RDD[T] = { parallelize(seq, numSlices) } |