Sort by

[return02]

Implement sort by transform by a very simple range_partitioner.

This algorithm is almost the same with Apache Spark: partition all the data into ordered partitions and sort them separately.

There're still some work to be done:

1. Find a better algorithm for building range_bounds.
2. implement descending.
3. use binary search in method get_partitions().
4. perhaps F: SerFunc(&Self::Item) -> K + Clone is better than F: SerFunc(Self::Item) -> K.
5. test corner case.

[iduartgomez]

Will review further later but could you rebase onto master (so cargo.lock change does not show) and run cargo fmt?

[return02]

Will review further later but could you rebase onto master (so cargo.lock change does not show) and run cargo fmt?

sorry. I'll rebase master and use cargo fmt later.