Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/11618#discussion_r55636107
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
---
@@ -62,6 +63,25 @@ abstract class QueryPlan[PlanType <:
QueryPlan[PlanType]] extends TreeNode[PlanT
}
/**
+ * Infers an additional set of constraints from a given set of equality
constraints.
+ * For e.g., if an operator has constraints of the form (`a = 5`, `a =
b`), this returns an
+ * additional constraint of the form `b = 5`
+ */
+ private def inferAdditionalConstraints(constraints: Set[Expression]):
Set[Expression] = {
+ constraints.map {
+ case eq @ EqualTo(l: Attribute, r: Attribute) =>
+ (constraints -- Set(eq)).map(_ transform {
+ case a: Attribute if a.semanticEquals(l) => r
+ }).union(
+ (constraints -- Set(eq)).map(_ transform {
+ case a: Attribute if a.semanticEquals(r) => l
+ }))
+ case _ =>
+ Set.empty[Expression]
+ }.foldLeft(Set.empty[Expression])(_ union _) -- constraints
--- End diff --
maybe not foldLeft -- most of the time fold is used it can be rewritten
into something imperative that is simpler (and a lot faster)
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