Repository: spark Updated Branches: refs/heads/master 38877ccf3 -> 9c40b9ead
misleading task number of groupByKey "By default, this uses only 8 parallel tasks to do the grouping." is a big misleading. Please refer to https://github.com/apache/spark/pull/389 detail is as following code : def defaultPartitioner(rdd: RDD[_], others: RDD[_]*): Partitioner = { val bySize = (Seq(rdd) ++ others).sortBy(_.partitions.size).reverse for (r <- bySize if r.partitioner.isDefined) { return r.partitioner.get } if (rdd.context.conf.contains("spark.default.parallelism")) { new HashPartitioner(rdd.context.defaultParallelism) } else { new HashPartitioner(bySize.head.partitions.size) } } Author: Chen Chao <crazy...@gmail.com> Closes #403 from CrazyJvm/patch-4 and squashes the following commits: 42f6c9e [Chen Chao] fix format 829a995 [Chen Chao] fix format 1568336 [Chen Chao] misleading task number of groupByKey Project: http://git-wip-us.apache.org/repos/asf/spark/repo Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/9c40b9ea Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/9c40b9ea Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/9c40b9ea Branch: refs/heads/master Commit: 9c40b9ead0d17ad836b3507c701198645c33d878 Parents: 38877cc Author: Chen Chao <crazy...@gmail.com> Authored: Wed Apr 16 17:58:42 2014 -0700 Committer: Reynold Xin <r...@apache.org> Committed: Wed Apr 16 17:58:42 2014 -0700 ---------------------------------------------------------------------- docs/scala-programming-guide.md | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/spark/blob/9c40b9ea/docs/scala-programming-guide.md ---------------------------------------------------------------------- diff --git a/docs/scala-programming-guide.md b/docs/scala-programming-guide.md index a07cd2e..2b0a51e 100644 --- a/docs/scala-programming-guide.md +++ b/docs/scala-programming-guide.md @@ -189,8 +189,8 @@ The following tables list the transformations and actions currently supported (s <tr> <td> <b>groupByKey</b>([<i>numTasks</i>]) </td> <td> When called on a dataset of (K, V) pairs, returns a dataset of (K, Seq[V]) pairs. <br /> -<b>Note:</b> By default, this uses only 8 parallel tasks to do the grouping. You can pass an optional <code>numTasks</code> argument to set a different number of tasks. -</td> +<b>Note:</b> By default, if the RDD already has a partitioner, the task number is decided by the partition number of the partitioner, or else relies on the value of <code>spark.default.parallelism</code> if the property is set , otherwise depends on the partition number of the RDD. You can pass an optional <code>numTasks</code> argument to set a different number of tasks. + </td> </tr> <tr> <td> <b>reduceByKey</b>(<i>func</i>, [<i>numTasks</i>]) </td>
