TODO.md

Differential dataflow to-do list:

1. Batch builders need an "ordered" option where the keys and vals are already sorted (cf group.output).

2. Several trace implementations need to be fleshed out (e.g. time and constant).

   • Consider ConstantCollection type which can only be construct from known data, arranged to constant.

3. Several trace implementations could benefit from a RHH keys field; prototype and test!

   • Probably wants a Uniform<T: Unsigned> struct for "node identifiers"; needs tweaks to Data trait.

4. Lots of sorting, but no radix-sorting. Historically a big improvement.

   • Connects to U: Unsigned output of hashed; no point radix-sorting u32 keys as if u64s.

5. Several operators need revision: distinct, threshold, cogroup.

6. The keys trace implementation has had zero testing. Important!

7. Progressive merging under-explored; trade-offs in rate of work? (yes, but worth?)

8. High-resolution times aren't too far away.

   • Think up alternate Collection type with new data bits.
   • Uncomment group implementation and get to work.

9. Join now has "deferred work"; check it out to see if it helps on large graphs.