refactor: simplify MapApi

[drmingdrmer]

I hereby agree to the terms of the CLA available at: https://databend.rs/dev/policies/cla/

Summary

refactor: simplify MapApi

• Add trait MapKey and MapValue to define behavior of key values
  that are used in MapApi.

• Add Ref and RefMut as container of reference to leveled data.

• Collect get() and range() implementation into function.

The MapApi trait can not be generalized to adapt arbitrary lifetime,
such as using self instead of &self: MapApiRO { fn get(self, key) }.
Because there is a known limitation with rust GAT and hihger ranked
lifetime: See: rust-lang/rust#114046

error: implementation of `MapApiRO` is not general enough
  --> src/meta/raft-store/src/sm_v002/sm_v002.rs:80:74
   |
80 |       async fn get_kv(&self, key: &str) -> Result<GetKVReply, Self::Error> {
   |  __________________________________________________________________________^
81 | |         let got = self.sm.get_kv(key).await;
82 | |
83 | |         let local_now_ms = SeqV::<()>::now_ms();
84 | |         let got = Self::non_expired(got, local_now_ms);
85 | |         Ok(got)
86 | |     }
   | |_____^ implementation of `MapApiRO` is not general enough
   |
   = note: `MapApiRO<'1, std::string::String>` would have to be implemented for the type `&'0 LevelData`, for any two lifetimes `'0` and `'1`...
   = note: ...but `MapApiRO<'2, std::string::String>` is actually implemented for the type `&'2 LevelData`, for some specific lifetime `'2`

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databend	⬜️ Ignored (Inspect)	Visit Preview		Sep 29, 2023 10:16am

[ariesdevil]

I read a blog the other day where the author had written a library that claimed to workaround lifetime problems, I'm not sure if it's useful or not.
The blog: https://sabrinajewson.org/blog/the-better-alternative-to-lifetime-gats
The crate: https://docs.rs/nougat/latest/nougat/

[drmingdrmer]

I read a blog the other day where the author had written a library that claimed to workaround lifetime problems, I'm not sure if it's useful or not. The blog: https://sabrinajewson.org/blog/the-better-alternative-to-lifetime-gats The crate: https://docs.rs/nougat/latest/nougat/

I sincerely appreciate your assistance!

[BohuTANG]

Happy Mid-Autumn Day!

[drmingdrmer]

Happy Mid-Autumn Day!

Happy National Day!

[drmingdrmer]

I read a blog the other day where the author had written a library that claimed to workaround lifetime problems, I'm not sure if it's useful or not. The blog: https://sabrinajewson.org/blog/the-better-alternative-to-lifetime-gats The crate: https://docs.rs/nougat/latest/nougat/

Quite good an article. It explains in detail the causes of the issue I have had, and provides a workaround solution.

The crate nougat building upon this workaround does not address my issue, though, because of the limitation of it:

• Only lifetime GATs are supported (no type Assoc nor type Assoc<const …>).