Github user mateiz commented on a diff in the pull request:
https://github.com/apache/spark/pull/727#discussion_r12511628
--- Diff: core/src/main/scala/org/apache/spark/rdd/RDD.scala ---
@@ -328,11 +328,20 @@ abstract class RDD[T: ClassTag](
def coalesce(numPartitions: Int, shuffle: Boolean = false)(implicit ord:
Ordering[T] = null)
: RDD[T] = {
if (shuffle) {
+ /** Distributes elements evenly across output partitions, starting
from a random partition. */
+ def distributePartition(index: Int, items: Iterator[T]):
Iterator[(Int, T)] = {
+ var position = (new Random(index)).nextInt(numPartitions)
+ items.map{ t =>
+ position = position + 1 % numPartitions
--- End diff --
This is going to mod the 1 with numPartitions and keep increasing
`position`, probably not exactly what we want. In reality passing just
`position` as the key would be fine, because the hashCode for it will be
position as well, and the Partitioner will mod that with `numPartitions`. No
need to mod twice.
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