peter-toth commented on code in PR #13467:
URL: https://github.com/apache/datafusion/pull/13467#discussion_r1848246474
##########
datafusion/common/src/tree_node.rs:
##########
@@ -769,6 +770,263 @@ impl<T> Transformed<T> {
}
}
+/// [`Container`] contains elements that a function can be applied on or
mapped. The
+/// elements of the container are siblings so the continuation rules are
similar to
+/// [`TreeNodeRecursion::visit_sibling`] / [`Transformed::transform_sibling`].
+pub trait Container<'a, T: 'a>: Sized {
+ fn apply_elements<F: FnMut(&'a T) -> Result<TreeNodeRecursion>>(
+ &'a self,
+ f: F,
+ ) -> Result<TreeNodeRecursion>;
+
+ fn map_elements<F: FnMut(T) -> Result<Transformed<T>>>(
+ self,
+ f: F,
+ ) -> Result<Transformed<Self>>;
+}
+
+impl<'a, T: 'a, C: Container<'a, T>> Container<'a, T> for Box<C> {
+ fn apply_elements<F: FnMut(&'a T) -> Result<TreeNodeRecursion>>(
Review Comment:
Actually, introducing `dyn FnMut` (trait objects) would mean dynamic
dispatch and so come with performance penalty. But trait alias
(https://doc.rust-lang.org/beta/unstable-book/language-features/trait-alias.html)
is an unstalbe feature so I'm not sure we can do this yet.
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