Jefffrey opened a new issue, #18670: URL: https://github.com/apache/datafusion/issues/18670
### Is your feature request related to a problem or challenge? `GenericDistinctBuffer` was introduced by #18348 to make it easier to write distinct accumulators. Currently it uses `Hashable` to represent the items being stored: https://github.com/apache/datafusion/blob/e42a0b626aa3b6b2e5e8b297c432e0c982706e8e/datafusion/functions-aggregate-common/src/utils.rs#L185-L188 https://github.com/apache/datafusion/blob/e42a0b626aa3b6b2e5e8b297c432e0c982706e8e/datafusion/functions-aggregate-common/src/utils.rs#L73-L81 `Hashable` is mainly required because `f32`/`f64` aren't hashable natively, so this wrapper lets us hash them + all other native types (e.g. `i32`, `u64`). However I wonder if there is a way to use `Hashable` only for floats, whilst using the native `Hash` implementation for other native types (potential performance benefit?). ### Describe the solution you'd like Be able to use `GenericDistinctBuffer` generically over both `f32` and `i32` types without needing to force both through `Hashable` interface. This could be done by having duplicated versions, one that takes `Hashable` and one that takes natively hashable types, but ideally want a single solution. - If we had specialization this would be much easier 😅 ### Describe alternatives you've considered _No response_ ### Additional context If we could get this to work, we could fold `PrimitiveDistinctCountAccumulator` together with `FloatDistinctCountAccumulator`: https://github.com/apache/datafusion/blob/e42a0b626aa3b6b2e5e8b297c432e0c982706e8e/datafusion/functions-aggregate-common/src/aggregate/count_distinct/native.rs#L44-L51 https://github.com/apache/datafusion/blob/e42a0b626aa3b6b2e5e8b297c432e0c982706e8e/datafusion/functions-aggregate-common/src/aggregate/count_distinct/native.rs#L126-L129 Also when making these changes we'd need to benchmark as likely there are performance implications; I initially tried forcing `PrimitiveDistinctCountAccumulator` to use `Hashable` but I kept hitting regressions on micro benchmark with `count(distinct)` queries, so need to keep that in mind. -- 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]
