alamb commented on code in PR #14038:
URL: https://github.com/apache/datafusion/pull/14038#discussion_r1905987391
##########
datafusion/physical-expr-common/src/sort_expr.rs:
##########
@@ -409,6 +409,22 @@ impl LexOrdering {
.map(PhysicalSortExpr::from)
.collect()
}
+
+ /// Collapse a `LexOrdering` into a new duplicate-free `LexOrdering` based
on expression.
+ ///
+ /// This function filters duplicate entries that have same physical
+ /// expression inside, ignoring [`SortOptions`]. For example:
+ ///
+ /// `vec![a ASC, a DESC]` collapses to `vec![a ASC]`.
+ pub fn collapse(self) -> Self {
+ let mut output = LexOrdering::default();
+ for item in self {
+ if !output.iter().any(|req| req.expr.eq(&item.expr)) {
+ output.push(item);
Review Comment:
In the original code this was `item.clone()` -- though it is only cloning an
Arc so the performance benefit is likely minimal
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