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A generic framework for on-demand, incrementalized computation. Inspired by adapton, glimmer, and rustc's query system.
fad97eeb6a
This had two unexpected consequences, one unfortunate, one "medium": * All `salsa::Database` must be `'static`. This falls out from `Q::DynDb` not having access to any lifetimes, but also the defaulting rules for `dyn QueryGroup` that make it `dyn QueryGroup + 'static`. We don't really support generic databases anyway yet so this isn't a big deal, and we can add workarounds later (ideally via GATs). * It is now statically impossible to invoke `snapshot` from a query, and so we don't need to test that it panics. This is because the signature of `snapshot` returns a `Snapshot<Self>` and that is not accessible to a `dyn QueryGroup` type. Similarly, invoking `Runtime::snapshot` directly is not possible becaues it is crate-private. So I removed the test. This seems ok, but eventually I would like to expose ways for queries to do parallel execution (matklad and I had talked about a "speculation" primitive for enabling that). * This commit is 99% boilerplate I did with search-and-replace. I also rolled in a few other changes I might have preferred to factor out, most notably removing the `GetQueryTable` plumbing trait in favor of free-methods, but it was awkward to factor them out and get all the generics right (so much simpler in this version). |
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| book | ||
| components/salsa-macros | ||
| examples | ||
| src | ||
| tests | ||
| .dir-locals.el | ||
| .gitignore | ||
| Cargo.toml | ||
| FAQ.md | ||
| LICENSE-APACHE | ||
| LICENSE-MIT | ||
| README.md | ||
| RELEASES.md | ||
salsa
A generic framework for on-demand, incrementalized computation.
Obligatory warning
Very much a WORK IN PROGRESS at this point. Ready for experimental use but expect frequent breaking changes.
Credits
This system is heavily inspired by adapton, glimmer, and rustc's query system. So credit goes to Eduard-Mihai Burtescu, Matthew Hammer, Yehuda Katz, and Michael Woerister.
Key idea
The key idea of salsa is that you define your program as a set of
queries. Every query is used like function K -> V that maps from
some key of type K to a value of type V. Queries come in two basic
varieties:
- Inputs: the base inputs to your system. You can change these whenever you like.
- Functions: pure functions (no side effects) that transform your inputs into other values. The results of queries is memoized to avoid recomputing them a lot. When you make changes to the inputs, we'll figure out (fairly intelligently) when we can re-use these memoized values and when we have to recompute them.
Want to learn more?
To learn more about Salsa, try one of the following:
- read the heavily commented
hello_worldexample; - check out the Salsa book;
- watch one of our videos.
Getting in touch
The bulk of the discussion happens in the issues and pull requests, but we have a zulip chat as well.