waynexia opened a new issue, #7765: URL: https://github.com/apache/arrow-datafusion/issues/7765
### Is your feature request related to a problem or challenge? `Expr::Wildcard` and `Expr::QualifiedWildcard` are expressions that reference all columns. But it seems redundant that we don't need a special expr type to do that. This issue proposes to remove these two expr kinds. ### Describe the solution you'd like Wildcard (`*`) can be expanded to concrete column lists when it appears. This manner seems viable in the three most common use cases I can come up with: - (1) generate plan from SQL AST. Some scenarios already acted like this. E.g., `select * from table` will generate a projection with all fields, rather than a wildcard expr. - (2) from `LogicalPlanBuilder` and (3) from `DataFrame`. In some aspects, these two entrances are the same. And both are strong typed (or strong schema-ed), which allows us to expand the wildcard immediately using the schema from current stage. Besides this, `Expr::Wildcard` is not properly handled in the codebase, because it's not a "first class" expr. Take some functions as examples: - `expr_to_columns`: from the correctness aspect, it should also count columns referenced by `Expr::Wildcard` and `Expr::QualifiedWildcard`. - `create_physical_name`: this function requires all the wildcards to be expanded before calling it. And I find another issue that related to `Wildcard`: https://github.com/apache/arrow-datafusion/issues/5473. The [solution](https://github.com/apache/arrow-datafusion/pull/5627) is to add an optimizer rule that expands all wildcards. This proposal is going to do something similar but in a more eager way. ### Describe alternatives you've considered _No response_ ### Additional context _No response_ -- 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]
