blog VS pond

This reminds me of a great blog post by Frank McSherry (Materialize, timely dataflow, etc) talking about how using the right tools on a laptop could beat out a bunch of these JVM distributed querying tools because... data locality basically.

https://github.com/frankmcsherry/blog/blob/master/posts/2015...

Oh, cool!

And yeah, licenses can be challenging and frustrating, especially the first time you release a major project.

I am really super excited by the idea of embedded Datalog in Rust. I run into a lot of situations where I need something that fits in that awkward gap between SQL and Prolog. I want more expressiveness, better composability, and better graph support than SQL. But I also want finite-sized results that I can materialize in bounded time.

There has been some very neat work with incrementally-updated Datalog in the Rust community. For example, I think Datafrog is really neat: https://github.com/frankmcsherry/blog/blob/master/posts/2018... But it's great to see more neat projects in this space, so thank you.

They used to but Frank McSherry (author of differential dataflow) wrote them a specialized version without all the dataflow infrastructure [1]. It's part of the rust-lang nursery [2] now but hasn't been updated in a while, so I'm not sure what happened to it.

[1] https://github.com/frankmcsherry/blog/blob/master/posts/2018...

[2] https://github.com/rust-lang/datafrog

Importantly, this doesn't just use memoization (it actually avoids having to spend memory on that), but rather uses operators (nodes in the dataflow graph) that directly work with `(time, data, delta)` tuples. The `time` is a general lattice, so fairly flexible (e.g. for expressing loop nesting/recursive computations, but also for handling multiple input sources with their own timestamps), and the `delta` type is between a (potentially commutative) semigroup (don't be confused, they use addition as the group operation) and an abelian group. E.g. collections that are iteratively refined in loops often need an abelian `delta` type, while monoids (semigroup + explicit zero element) allow for efficient append-only computations [0].

[0]: https://github.com/frankmcsherry/blog/blob/master/posts/2019...

We used to use a library called Pond.js, https://github.com/esnet/pond, but the reliance on Immutable.JS caused some performance pitfalls, so we wrote a system from scratch that deals with data in a batched streaming fashion. A lot of the concepts were borrowed from a Rust library called timely-dataflow, https://github.com/TimelyDataflow/timely-dataflow.