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Manishearth / elsa

Append-only collections for Rust where borrows to entries can outlive insertions
Apache License 2.0
228 stars 33 forks source link

Set (and map) types that implement `Sync`? #71

Closed jplatte closed 1 year ago

jplatte commented 1 year ago

Hi! I just found out about this crate because I wanted to keep track of which directories were created and which files were written by a parallel static site generator I'm working on and an append-only set seemed like a good solution that's potentially more efficient than a regular set behind a mutex.

While I couldn't find an append-only set anywhere, elsa at least offers append-only map types, and it seems like it would be trivial to build set types on top. However, I noticed that both map types don't implement Sync, which makes them no better than std types for my use case.

Am I wrong to think that an append-only set would be the right tool for my use case? Are Sync set and map types possible (such that they perform better than a mutex-protected map or set) and in-scope for this crate?

Manishearth commented 1 year ago

We have these already https://docs.rs/elsa/latest/elsa/sync/index.html

No set types but I'd accept a PR wrapping the map type into a set.

Also for sets just an RWLock<Set> is fine, the key value proposition of elsa isn't relevant for sets because sets don't produce references anyway.

jplatte commented 1 year ago

Okay, thanks for the quick reply!

Likely irrelevant remark: I don't think an RwLock instead of a Mutex is right for my use case (AFAICT the only operation I'm going to need is insert, to check if the value was already present and insert it if not).

Manishearth commented 1 year ago

Yeah the kind of synchronization depends on your use case. Mutices are fine overall