How to get a sample with an exact sample size in Spark RDD?

Question

Why does the rdd.sample() function on Spark RDD return a different number of elements even though the fraction parameter is the same? For example, if my code is

Answer 1

Another way can be to first takeSample and then make RDD. This might be slow with large datasets.

sc.makeRDD(a.takeSample(false, 1000, 1234))