junlincc commented on pull request #15798: URL: https://github.com/apache/superset/pull/15798#issuecomment-884402736
"I don’t recommend doing count_distinct for string column. This is a precise deduplication operation. It is very resource intensive for the database. imagine, if this column has many values(high cardinality), this query can easily crash the database. some databases have special functions to do this calculation." @zhaoyongjie I dont think this should be a concern. Even there's a preselected aggregate, users still need to click SAVE and RUN to run query that potentially crush anything. From UX standpoint, having a preselected aggregate has the equal amount of clicks to no preselected if users need to choose COUNT instead. and for most cases, count_distinct is indeed what users choose for STRING columns. I don't see any reasons why we should use COUNT as preselected. -- 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]
