ordering

[piccolbo]

In a distributed context, with the data in general partitioned, it's not clear what it means to sort exactly. In the case of terasort, it means that the data is partitioned by range and then sorted within each partition. What are alternatives to ordering and what are the use cases that these solve? Hive has an order by and sort by. Sort is within each reducer. Order has to be followed by a limit clause, which makes it equivalent to top k, which plyrmr has already.