alamb opened a new pull request, #20193: URL: https://github.com/apache/datafusion/pull/20193
## Which issue does this PR close? - Part of https://github.com/apache/datafusion/issues/20173 ## Rationale for this change I am going through how the various layers of expression pushdown and schema rewrites work, and I spent a long time confused about what the `sync_with_child` parameter on `update_expr(.., true)` vs `update_expr(..., false)` did After some study I realized it controls which way the rewrite is done (either project the expressions to refer to the projection expressions, or the opposite, 'unproject' an expression) ## What changes are included in this PR? <!-- 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? Yes by existing ci ## Are there any user-facing changes? There are new APIs, but no changes to existing APIs -- 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]
