Github user mengxr commented on a diff in the pull request: https://github.com/apache/spark/pull/1025#discussion_r13578489 --- Diff: core/src/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala --- @@ -156,6 +161,182 @@ class PairRDDFunctions[K, V](self: RDD[(K, V)]) } /** + * Return a subset of this RDD sampled by key (via stratified sampling). + * We guarantee a sample size = math.ceil(fraction * S_i), where S_i is the size of the ith --- End diff -- Also, it would be good to put a comment saying that this method requires two passes.
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