What is the most efficient way in Spark to get unique pairs in a PairRDD?
<p>Given an <code>initial: PairRDD[(Long, Long)]</code>, what is the most efficient method to get an <code>other: PairRDD[(Long, Long)]</code> which contains each pair of <code>initial</code> exactly once? (i.e. filters out duplicate pairs.)</p>

<p>Specifically, is there something more efficient than <code>initial.distinct()</code>?</p>