urlyy commented on PR #2898:
URL: https://github.com/apache/fory/pull/2898#issuecomment-3535278973
Can we modify the format of `version_hash`?
The reason is that Rust needs to compute the `version_hash` at compile time
for different compression scenarios, which requires calculating **$2^5$**
hashes (because of compress_i32 / not_compress_i32 / not_compress_i64 /
compress_to_var_i64/ compress_to_sli_i64`). If we further add `U32 / VAR_U32 /
U64 / VAR_U64 / SLI_U64`, it becomes even more explosive.
Separating the two compression flags can effectively mitigate this situation.
Which means, for `int_32` and `int_64`, when computing the hash, we only
treat them as `Types::INT32` and `Types::INT64`. Then, after finishing the loop
over all fields,
```rust
for field in fields {
fingerprint.push_str(&effective_type_id.to_string());
fingerprint.push(',');
fingerprint.push_str(if *nullable { "1;" } else { "0;" });
}
```
we can append:
```rust
fingerprint.push_str(if type_resolver.compress_int { "1;" } else { "0;" });
fingerprint.push_str(format!("{};", type_resolver.long_encoding as i16));
```
to add compress_flag information to hash value.
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