vogievetsky commented on issue #10586: URL: https://github.com/apache/druid/issues/10586#issuecomment-739435823
Your understanding is correct! if `UserId` is a dimensions then a sketch(UserId) would always represent just one UserId. It is maybe not the best example. There is still a reason you might want to do it - for performance! In short `APPOX_COUNT_DISTINCT(userId_sketch)` would computer faster than `APPOX_COUNT_DISTINCT(userId)` as the userId_sketch is already semi-digested even if it is just for that one user_id. Since Druid users love performance more than they love their mother it is not uncommon to see this pattern. ---------------------------------------------------------------- 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. For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
