plan.txt

https://docs.rs/tokio/latest/tokio/sync/mpsc/fn.channel.html

https://docs.rs/substrait/latest/substrait/proto/rel/enum.RelType.html

            Operator G
                |
                |
            Channel C
                |
                |
            Operator P -> waits for Op1, then builds hash table
          /            \
    Channel A         Channel B
       /                  \
      /                    \
Operator 1              Operator 2

Operator P pseudo:
    listen on channel A, listen on channel B

    when it has what it needs
    spin up rayon threads
    wait on rayon threads to finish
    send on channel C

Brain: 
   takes in substrait
   interprets it
   and starts whipping tokio threads for each op, don't need to wait cuz tokio = amazing light weight
   + make channels for all edges in the DAG


- Note: Create the threads for each operator top down
- data is then pushed up



tokio: 10000 light-weight threads

rayon: a few OS threads