Top R sorting in PySpark

[magsol]

The PySpark API provides a couple of sorting primitives:

• repartitionAndSortWithinPartitions
• sortBy
• sortByKey
• takeOrdered

The last one in particular looks promising for our uses (here's a StackOverflow question on its use).

[magsol]

This actually is not needed, since the topR operation is performed on a vector, which will be held in memory.