To get the most complete introduction to Salsa's inner workings, check out the "How Salsa Works" video. If you'd like a deeper dive, the "Salsa in more depth" video digs into the details of the incremental algorithm.
The key idea of
salsa is that you define your program as a set of
queries. Every query is used like a function
K -> V that maps from
some key of type
K to a value of type
V. Queries come in two basic
- 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 are 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.
Using Salsa is as easy as 1, 2, 3...
- Define one or more query groups that contain the inputs and queries you will need. We'll start with one such group, but later on you can use more than one to break up your system into components (or spread your code across crates).
- Define the query functions where appropriate.
- Define the database, which contains the storage for all the inputs/queries you will be using. The query struct will contain the storage for all of the inputs/queries and may also contain anything else that your code needs (e.g., configuration data).
To see an example of this in action, check out the
example, which has a number of comments explaining how
Check out the plumbing chapter to see a deeper explanation of the code that Salsa generates and how it connects to the Salsa library.