2010YOUY01 commented on issue #26696: URL: https://github.com/apache/datafusion/issues/26696#issuecomment-6379686428
> On ClickBench `hits_partitioned` with dictionary reads enabled, grouping on a high-cardinality dictionary column is 2.6x slower than grouping on the same column cast to `Utf8`: I think dictionary encoding is an optimization opportunity for low-cardinality keys, this purposed change looks like letting operator to fix the consequence of choosing the pathological encoding. If dictionary array start to get preserved into execution, I think it's okay to assume them to have very low cardinality, and slicing/recomputing on key sets has negligible overhead. (storage/parquet might keep higher cardinality dictionaries) -- 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]
