freshtonic commented on issue #934: URL: https://github.com/apache/datafusion-sqlparser-rs/issues/934#issuecomment-2841810444
@ramnes thank you for clarifying! I'm 100% in favour of any style of `Visitor` implementation that covers all AST node types in `sqlparser`. I'm less fussy than I used to be about the particular approach taken. These are the "obvious" approaches to me: 1. Big `Visitor` trait (enter/exit or pre/post methods for _every_ AST node type) 2. Small `Visitor` trait (just enter/exit methods, e.g. `fn enter<N: Visitable>(&mut self, node: &N) -> ControlFlow` 3. Small generic `Visitor<N: Visitable>` trait (just enter/exit methods, e.g. `fn enter(&mut self, node: &N) -> ControlFlow` Option 1 is (subjectively) ugly but gets the job done. Option 2 has a cleaner trait but implementations must downcast the node to do anything useful with it. Option 3 is just as clean as 2 and downcasting is no longer required in every implementation, _but_ `Visitor` dispatch no longer works because the AST traversal has to be able to dispatch _any_ node type to a `Visitor`, so you still need an additional dispatch mechanism. This is where the enum based dispatch could help. The approach to `Visitor` I ended up going with in `sqltk` is essentially Option 2 above and looks like [this](https://docs.rs/sqltk/latest/sqltk/trait.Visitor.html). I have been thinking about alternative approach to avoid all of the explicit casting and just generate the code. Here's the [playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=f1d842d0b5a9d4af39a4684ffc41265a) -- 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: github-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
