Dandandan commented on PR #20481: URL: https://github.com/apache/datafusion/pull/20481#issuecomment-4013754792
> I actually think we could do this fairly efficiently (with relatively low ovehead) using the RowSelection API -- aka fetch the data for a single Row Group but then potentially break that row group up into several smaller morsels (e.g. 10-20 batches worth of rows) 🤔 Yes that was my idea as well. > I was playing around with the opposite: the idea that we'd pack multiple row groups into a morsel if they are small. I feel that ideally a morsel would be defined in terms of ~ units of work (which is difficult because we'd have one metric for both CPU and IO work; maybe "bytes to scan" is good enough) and not row groups or rows. So if row groups are small we pack several into 1 morsel. If row groups are large we split them up into multiple morsels using RowSelection. Going the other way around if they are small might also be great, nice idea. Another consideration is dynamic filters: if we start smaller, we could in some cases avoid more IO early on. -- 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]
