alamb commented on issue #5325: URL: https://github.com/apache/arrow-datafusion/issues/5325#issuecomment-1441767680
> approx size(first scalar value size * len()) improves up to 10 times, but not accurate size for variable length, like strings Thank you for looking into this @comphead I think we should definitely use this approach for fixed length (non variable length) data -- it will solve the performance regression we saw for clickbench In terms of handling variable length data more efficiently, I am not sure it is worth a lot of time optimizing the `size()` implementation because my guess is that the `size()` calculation will be a smaller portion of the overall runtime for high cardinality string columns (each one will be an allocated string, for example). I think a separate project to handle `COUNT DISTINCT(high_cardinality_string_column)` is probably needed Thus I propose: 1. Implement the simplest thing that fixes the clickbench performance regression 2. File a follow on ticket to track further improving the performance of COUNT DISTINCT queries (I can do this) -- 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]
