berkaysynnada commented on code in PR #14038:
URL: https://github.com/apache/datafusion/pull/14038#discussion_r1906682942
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datafusion/physical-expr-common/src/sort_expr.rs:
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@@ -540,6 +557,33 @@ impl LexRequirement {
.collect(),
)
}
+
+ /// Constructs a duplicate-free `LexOrderingReq` by filtering out
+ /// duplicate entries that have same physical expression inside.
+ ///
+ /// For example, `vec![a Some(ASC), a Some(DESC)]` collapses to `vec![a
+ /// Some(ASC)]`.
+ ///
+ /// It will also filter out entries that are ordered if the next entry is;
+ /// for instance, `vec![floor(a) Some(ASC), a Some(ASC)]` will be
collapsed to
+ /// `vec![a Some(ASC)]`.
+ pub fn collapse(self) -> Self {
+ let mut output = Vec::<PhysicalSortRequirement>::new();
+ let mut exprs = IndexSet::new();
+ let mut reqs = vec![];
+ for item in self {
+ let PhysicalSortRequirement { expr, options: req } = item;
+ // new insertion
+ if exprs.insert(expr) {
+ reqs.push(req);
+ }
+ }
+ debug_assert_eq!(reqs.len(), exprs.len());
+ for (expr, req) in izip!(exprs, reqs) {
+ output.push(PhysicalSortRequirement::new(expr, req));
+ }
+ LexRequirement::new(output)
+ }
Review Comment:
I realized https://github.com/alamb/datafusion/pull/27 now, and makes sense.
So, why do we apply the same in LexOrdering::collapse()?
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