goldmedal opened a new pull request, #16540: URL: https://github.com/apache/datafusion/pull/16540
## Which issue does this PR close? <!-- We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example `Closes #123` indicates that this PR will close issue #123. --> No corresponding issue at DataFusion. I encountered it in the Wren AI case. - https://github.com/Canner/wren-engine/issues/1089 ## Rationale for this change Consider the following SQL: ``` select count(*) from (select 1) ``` It will be simplified to the following SQL after we move `CountWildcardRule` to the logical planner https://github.com/apache/datafusion/pull/14689 ``` SELECT count(1) AS \"count(*)\" FROM (SELECT 1) ``` However, some dialects (e.g. BigQuery) don't allow some [special characters](https://cloud.google.com/bigquery/docs/schemas#flexible-column-names)(`(`, `*`, `@`, ...) in an alias name. We should have a way to handle this case for the unparser. <!-- Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed. Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes. --> ## What changes are included in this PR? - Introduce the interface `col_alias_overrides` for the unparser dialect. ```rust /// Allows the dialect to override column alias unparsing if the dialect has specific rules. /// Returns None if the default unparsing should be used, or Some(String) if there is /// a custom implementation for the alias. fn col_alias_overrides(&self, _alias: &str) -> Result<Option<String>> { Ok(None) } ``` - Add `BigQueryDialect`, which will encode the special character in the alias name. <!-- There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR. --> ## Are these changes tested? - Add the unit test. - This change comes from Wren AI fork https://github.com/Canner/datafusion/pull/1 which is used in the production for a while. It works well. <!-- We typically require tests for all PRs in order to: 1. Prevent the code from being accidentally broken by subsequent changes 2. Serve as another way to document the expected behavior of the code If tests are not included in your PR, please explain why (for example, are they covered by existing tests)? --> ## Are there any user-facing changes? <!-- If there are user-facing changes then we may require documentation to be updated before approving the PR. --> <!-- If there are any breaking changes to public APIs, please add the `api change` label. --> -- 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
