Point to insert_unique in code comment for IdOrdMap::from_iter_unique#300
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Hello, again! 👋 While I was reading about `IdOrdMap::from_iter_unique` and writing up #300, it occurred to me that the method might be doing extra work. Specifically, it _seems_ like we're checking for duplicates twice: - the first check happens in `map.entry(value.key())` and that tells us whether this is a duplicate. - the second check happens in the `Entry::Vacant` branch (i.e. after we already determined that this is not a duplicate) when `entry.insert_ref(value)` is called. `insert_ref` [calls `insert_unique_impl`](https://github.com/oxidecomputer/iddqd/blob/82bbad02fc3a60283fd12495334a6ee16d81f248/crates/iddqd/src/id_ord_map/entry.rs#L162-L170) which [also checks for duplicates](https://github.com/oxidecomputer/iddqd/blob/82bbad02fc3a60283fd12495334a6ee16d81f248/crates/iddqd/src/id_ord_map/imp.rs#L1470-L1492). ```rust for value in iter { match map.entry(value.key()) { // <---- first check Entry::Occupied(entry) => { // return error for duplicate } Entry::Vacant(entry) => { entry.insert_ref(value); // <---- second check nested inside } } } ``` So, if I understood things correctly, we're checking for duplicates twice for a single unique-key insert, and once should be enough. This PR is an attempt at a minimal change to avoid that extra work: extract the insertion logic out of `insert_unique_impl` so that it can be reused. This new method, `insert_known_unique_impl` (naming suggestions always welcome 🙈), is private and assumes that it doesn't need to check for duplicates itself because that has been done by the callers. This method is what we then call from both `insert_unique_impl` and `from_iter_unique` after those methods determined that the value's key is unique. And that then removes the extra check for duplicates in `from_iter_unique`. Again, I tried to start with a minimal diff, and if the general idea makes sense and feels valuable -- happy to iterate on the implementation based on feedback! --------- Co-authored-by: Rain <rain@oxide.computer>
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👋 Hello! I was reading some code using
IdOrdMapand then went on to read some ofIdOrdMap's implementation bits.As I was reading a comment in
from_iter_unique(side-note: many thanks for leaving useful comments like that -- I was wondering about exactly the thing the comment talks about), I was a bit confused by it referring toinsert_overwriteas the "would be nice if we could use this" idea. I think it should be referring toinsert_uniqueinstead. So, I'm doing my open-source duty and offering a tiny PR to update this.Apologies for the noise if I misunderstood things!