Commits on Sep 27, 2022

1. Introduce fate …

   Previously I made the questionable API design of having
   `StatefulLogic::snapshot` return a `StateUpdate`. This meant that the
   snapshotting process affected the behavior of the stateful operator,
   since it could return `Reset` to signal up to `StatefulUnary` to
   discard the logic.
   
   This unwinds that tangle by introducing a new method with a perhaps
   overly poetic name `StatefulLogic::fate` which should return what
   `StatefulUnary` should do with the logic when it's done processing via
   a `LogicFate` enum: either `Retain` it or `Discard` it.
   
   `fate` is attempting to encapsulate the problem of `StatefulUnary` is
   the owner of the logics, so they can't drop themselves.
   
   This is nice because it simplifies the return value of `exec` to just
   output. The awaken delay is handled in `fate`.
   
   The other part of the logic return value was "time to next
   awake". Which is now encapsulated in `StatefulLogic::next_awake`.
   
   It also breaks apart the results of `Windower` due to the same kind of
   problem: the `WindowStatefulLogic` is the owner, and we need to
   communicate back when it's safe to discard a `Windower`. Adds
   `Windower::is_empty` and `Windower::next_close` to handle this. This
   fixes the bug of never discarding window state if a key is never seen
   again: we now discard that state whenever all windows for a key are
   closed.
   
   A few other small changes:
   
   - Standardises on the language of "awaken" a logic. Still uses
     Timely's "activate" for a Timely operator, though. Renames
     `StatefulLogic::exec` to `StatefulLogic::on_awake` to make more
     explicit when it is called. Renames `WindowLogic::exec` to
     `WindowLogic::with_next` to make explicit when it's called.
   
   - Clarifies more comments in the giant chunk of code for
     `StatefulUnary::stateful_unary`. I was also able to optimize it a
     little and get rid of two of our temporary buffers. I think it makes
     the process slightly clearer.

   

   davidselassie committed Sep 27, 2022
   Copy the full SHA

   a26045a View commit details

   Browse the repository at this point in the history