That's fine with me, but Julian pointed out many difficulties that arise in cases I had not considered. Let's see if these will be an obstacle in practice.
Mihai ________________________________ From: Yanjing Wang <zhuangzixiao...@gmail.com> Sent: Friday, June 27, 2025 12:11 AM To: dev@calcite.apache.org <dev@calcite.apache.org> Subject: Re: Re: [DISCUSS] Preserving Output Alias Names After RelNode Optimization Thank you for your detailed response. Given that consistent column naming is a common challenge across organizations using Apache Calcite planner, I believe we should establish a standardized approach. End users expect predictable column aliases in query results, regardless of the optimization process. Your proposed utility method for Calcite is promising. To formalize this solution, I suggest we: 1. Document this as the recommended best practice 2. Integrate it into planner.findBestExp method, which would provide a centralized point for handling column alias preservation This standardization would benefit all Calcite implementations by providing a consistent and reliable way to handle column aliases throughout the optimization process. Julian, Mihai, would you agree with this approach? suibianwanwan <suibianwanwa...@foxmail.com> 于2025年6月26日周四 18:07写道： > 1. I think so. > > 2. In my view, as long as we ensure the top-level Project is restored > after Planner (some Calcite users might output RelNode), it should be fine. > > 3. RelBuilder#Project will optimize identity nodes. You can set force=true > to force building a Project or directly call LogicalProject#create. > > I think we can add this utility method in Calcite: > 1. When the top level is a Project, merge the Project to preserve aliases > 2. When the top level is a Sort, call this method on its input > 3. For other cases, directly add a Project to restore aliases > > On 2025/06/26 07:24:48 Yanjing Wang wrote: > > > > > > > > > Dear Julian and Mihai, Thank you both for your detailed and insightful > > > responses. I'd like to confirm my understanding: 1. Regarding column > name > > > preservation approach: - If I understand correctly, using RelRoot to > get a > > > projected rel node of the best rel would be the recommended way to > preserve > > > column names of rel after optimization? 2. About subquery generation: > - I > > > see that subquery generation is controlled by RelToSqlConverter, so I > > > should focus on making adjustments there to control the subquery > generation > > > behavior for Project <- Sort rel pattern. 3. One observation I'd like > to > > > share: - I noticed that when I tried using a rel builder to add a > project > > > to the best rel (specifically when the best rel is a sort), adding a > > > project to the sort input rel doesn't seem to make a difference in the > > > outcome. Could you please confirm if my understanding aligns with your > > > suggestions? This would help ensure I'm moving in the right direction > with > > > the implementation. Best regards, Yanjing > > >
