Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/17899#discussion_r147546887
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -610,6 +611,25 @@ object CollapseWindow extends Rule[LogicalPlan] {
}
/**
+ * Transpose Adjacent Window Expressions.
+ * - If the partition spec of the parent Window expression is compatible
with the partition spec
+ * of the child window expression, transpose them.
+ */
+object TransposeWindow extends Rule[LogicalPlan] {
+ private def compatibleParititions(ps1 : Seq[Expression], ps2:
Seq[Expression]): Boolean = {
+ ps1.length < ps2.length &&
ps2.take(ps1.length).permutations.exists(ps1.zip(_).forall {
+ case (l, r) => l.semanticEquals(r)
+ })
+ }
+
+ def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
+ case w1 @ Window(we1, ps1, os1, w2 @ Window(we2, ps2, os2, grandChild))
--- End diff --
Just to ensure the results are still the same with and without the rule.
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