alamb commented on code in PR #16185:
URL: https://github.com/apache/datafusion/pull/16185#discussion_r2110078689
##########
datafusion/physical-expr/src/equivalence/class.rs:
##########
@@ -422,6 +423,60 @@ impl EquivalenceGroup {
self.bridge_classes()
}
+ /// Returns a set of all adjacent expression pairs in this equivalence
group.
+ ///
+ /// For each equivalence class, this function creates pairs of expressions
that are adjacent
+ /// to each other. For example, if we have an equivalence class [a, b, c],
it will generate
+ /// pairs (a,b), (a,c), (b,c) and their reverse pairs (b,a), (c,a), (c,b).
+ ///
+ /// This is used by the `intersect` function to find common expression
pairs between
+ /// two equivalence groups.
+ #[allow(clippy::type_complexity)]
+ fn adjacent_set(&self) -> HashSet<(&Arc<dyn PhysicalExpr>, &Arc<dyn
PhysicalExpr>)> {
+ let mut set = HashSet::new();
Review Comment:
this algorithm is `O(N^2)` in the number of items in the equivalence class,
right?
We have hit other really long planning times when using such algorithms, for
example
- https://github.com/apache/datafusion/issues/13748
Is there some way to make this more efficient? Maybe by creating an 2x
boolean array to represent the intersections?
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