clintropolis commented on issue #11659: URL: https://github.com/apache/druid/issues/11659#issuecomment-913247290
> Maybe the problem has to do with the special way that Druid handles the sys tables? Maybe they are not "really" tables? Maybe some documentation would help to say that "here is a list of Druid SQL features not supported in system tables..." This is actually true, currently Druid's system tables are not processed at all by the Druid native query engine, which produces some differing behavior in SQL queries depending on the tables involved. This is something we would like to change someday for a lot of reasons, this being one of the biggest ones, but we haven't got to it yet and it has a few blockers, such as the ability to order native Druid scan queries by columns other than time. This is documented, but it isn't perhaps as prominent as it could be: https://druid.apache.org/docs/latest/querying/sql.html#unsupported-features, nor it is exhaustive about the complete set of differences between the 2 implementations. >Druid claims to support SQL, and SQL is a standard. Supporting SQL means supporting the standard with, of course, the subtle adjustments and variations needed for each system. The standard was created as an aggregation of many use cases: the standard reviewed and supported those use cases so that each vendor doesn't have to repeat that process. And, as a user, if Druid claims to support SQL, then I should be able to use my knowledge of SQL with Druid without having to justify each SQL feature I might want to use. I think we strive to support SQL in a standard manner, but it is a bit of an ever-going work in progress (which to be fair to some extent could maybe be said of every database which claims to support SQL, since there is quite a lot of variety in behavior between different implementations in my experience 😅 ). I think we welcome any reports on where we differ from the SQL standard so that we can try to fix the issue, or document it in cases where it might not be possible without some non-trivial effort. I this specific case i wonder if it _is_ related to this being done against the system tables. Do you see the same behavior if you use a similar query on a native Druid table? -- 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]
