alamb commented on code in PR #5092:
URL: https://github.com/apache/arrow-datafusion/pull/5092#discussion_r1091075063
##########
datafusion/expr/src/expr_rewriter.rs:
##########
@@ -519,6 +495,49 @@ pub fn unnormalize_cols(exprs: impl IntoIterator<Item =
Expr>) -> Vec<Expr> {
exprs.into_iter().map(unnormalize_col).collect()
}
+struct RewriterAdapter<F> {
+ f: F,
+}
+
+impl<F> ExprRewriter for RewriterAdapter<F>
+where
+ F: FnMut(Expr) -> Result<Expr>,
+{
+ fn mutate(&mut self, expr: Expr) -> Result<Expr> {
Review Comment:
That is an interesting idea. What usecase do you have in mind?
Since `mutate` takes the expr by ownership (rather than by reference), I
think returning `expr` would be the same as not changing the original `expr`
(perhaps the same as returning `None`?)
However, I do wonder what actually happens when rewriting Boxed exprs 🤔
maybe they are still copied
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