chaokunyang opened a new issue, #1936: URL: https://github.com/apache/fury/issues/1936
### Feature Request Implement chunk based map predictive protocol, which is 2x faster than current one. > All Map serializers must extend `AbstractMapSerializer`. Format: ``` | length(unsigned varint) | key value chunk data | ... | key value chunk data | ``` #### map key-value chunk data Map iteration is too expensive, Fury won't compute the header like for list since it introduce [considerable overhead](https://github.com/apache/fury/issues/925). Users can use `MapFieldInfo` annotation to provide the header in advance. Otherwise Fury will use first key-value pair to predict header optimistically, and update the chunk header if the prediction failed at some pair. Fury will serialize the map chunk by chunk, every chunk has 255 pairs at most. ``` | 1 byte | 1 byte | variable bytes | +----------------+----------------+-----------------+ | chunk size: N | KV header | N*2 objects | ``` KV header: - If track key ref, use the first bit `0b1` of the header to flag it. - If the key has null, use the second bit `0b10` of the header to flag it. If ref tracking is enabled for this key type, this flag is invalid. - If the key types of map are different, use the 3rd bit `0b100` of the header to flag it. - If the actual key type of the map is not the declared key type, use the 4rd bit `0b1000` of the header to flag it. - If track value ref, use the 5th bit `0b10000` of the header to flag it. - If the value has null, use the 6th bit `0b100000` of the header to flag it. If ref tracking is enabled for this value type, this flag is invalid. - If the value types of the map are different, use the 7rd bit `0b1000000` header to flag it. - If the value type of map is not the declared value type, use the 8rd bit `0b10000000` of the header to flag it. If streaming write is enabled, which means Fury can't update written `chunk size`. In such cases, map key-value data format will be: ``` | 1 byte | variable bytes | +----------------+-----------------+ | KV header | N*2 objects | ``` `KV header` will be a header marked by `MapFieldInfo` in java. For languages such as golang, this can be computed in advance for non-interface types most times. The implementation can generate different deserialization code based read header, and look up the generated code from a linear map/list. #### Why serialize chunk by chunk? When fury will use first key-value pair to predict header optimistically, it can't know how many pairs have same meta(tracking kef ref, key has null and so on). If we don't write chunk by chunk with max chunk size, we must write at least `X` bytes to take up a place for later to update the number which has same elements, `X` is the num_bytes for encoding varint encoding of map size. And most map size are smaller than 255, if all pairs have same data, the chunk will be 1. This is common in golang/rust, which object are not reference by default. Also, if only one or two keys have different meta, we can make it into a different chunk, so that most pairs can share meta. The implementation can accumulate read count with map size to decide whether to read more chunks. ### Is your feature request related to a problem? Please describe _No response_ ### Describe the solution you'd like _No response_ ### Describe alternatives you've considered _No response_ ### Additional context #925 -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
