jayzhan211 commented on issue #15676: URL: https://github.com/apache/datafusion/issues/15676#issuecomment-2796621637
> Just to clarify, what does "order-preserved" mean exactly? Does it only refer to a single partition with ordered input, or can the order be determined by ORDER BY fields? The input of first/last is the same as the data in data source. > I don't understand why we should "return the first value among those "last values" with the same ordering keys". If the ordering keys are the same, the result may still be non-deterministic unless the input is ordered and in a single partition. This case is single partition (order-preserved) + ordering. To be more specifically, whether the output is deterministic depends on the sort algorithm, if we have stable sort where the order is preserved for same keys, then we have deterministic output. -- 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: github-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
