Very slow deserialization

[meghboltanic]

I found that in practice, use of DoubleArrayAhoCorasick::<V>::deserialize_unchecked() can be extremely slow. It typically takes 4-5s on my m1 (16gb ram) machine.

Here are some stats:

heap_bytes=90855648 // .heap_bytes()
num_states=7440593  // .num_states()

2023-12-11T01:35:52.049237Z  INFO load_index{index_file="index.bin"}:load:deserialize
2023-12-11T01:35:56.495537Z  INFO ...

[meghboltanic]

I'm happy to add serde's Serialize, and Deserialize trait (maybe under create's feature serde). I was able to get this to ~1s with Serde. Also, if we do this, we can skip unsafe. Let me know - happy to create a patch PR.

[vbkaisetsu]

@ezkangaroo The DoubleArrayAhoCorasick structure internally uses unsafe functions, so I don't want to implement Serialize and Deserialize traits.
Instead, it is possible to use serde internally and provide a deserialization API as an unsafe function.

You are welcome to write a pull request!

[vbkaisetsu]

Tip.

Although deserialize itself is a safe process, there is no guarantee that the automaton is correct, and in some cases memory access violations will occur, so the function must be unsafe to notify the user.

This is similar to String::from_utf8_unchecked, etc.