Github user hvanhovell commented on a diff in the pull request:
https://github.com/apache/spark/pull/13116#discussion_r63422967
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala ---
@@ -1494,6 +1493,56 @@ class Dataset[T] private[sql](
}
/**
+ * Returns a new [[Dataset]] by sampling a fixed num of rows, using a
random seed.
+ *
+ * @param withReplacement Sample with replacement or not.
+ * @param num num of rows to generate.
+ * @param seed Seed for sampling
+ * @return the sampling [[Dataset]]
+ */
+ def takeSample(withReplacement: Boolean, num: Int, seed: Long):
Dataset[T] = {
+ val numStDev = 10.0
+ require(num >= 0, "Negative number of elements requested")
+ require(num <= (Int.MaxValue - (numStDev *
math.sqrt(Int.MaxValue)).toInt),
+ "Cannot support a sample size > Int.MaxValue - " +
+ s"$numStDev * math.sqrt(Int.MaxValue)")
+ if (num == 0) {
+ sqlContext.createDataset[T](Seq())
+ } else {
+ val initialCount = this.count()
+ if (initialCount == 0) {
+ sqlContext.createDataset[T](Seq())
+ } else {
+ val rand = new Random(seed)
+ if (!withReplacement && num >= initialCount) {
+
sqlContext.createDataset[T](Utils.randomizeInPlace(this.collect(), rand))
+ } else {
+ val fraction = SamplingUtils.computeFractionForSampleSize(num,
initialCount,
+ withReplacement)
+ var samples = this.sample(withReplacement, fraction,
rand.nextInt()).collect()
+ var numIters = 0
+ while (samples.length < num) {
--- End diff --
Infinite loop if the user requests more rows than in the dataset.
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