Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/11565#discussion_r55776014
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -384,9 +378,21 @@ object ColumnPruning extends Rule[LogicalPlan] {
// Eliminate no-op Projects
case p @ Project(projectList, child) if sameOutput(child.output,
p.output) => child
+ // Eliminate no-op Window
+ case w: Window if w.windowExpressions.isEmpty => w.child
+
// Can't prune the columns on LeafNode
case p @ Project(_, l: LeafNode) => p
+ // Prune windowExpressions and child of Window
+ case p @ Project(_, w: Window) if (w.outputSet --
p.references).nonEmpty =>
+ val newWindowExprs =
w.windowExpressions.filter(p.references.contains)
--- End diff --
After rethink about it, seems we can still separate it into 2 rules.
We can add a `def windowOutputSet =
AttributeSet(windowExpressions.map(_.toAttribute))` to `Window` operator, and
change the first case to `case p @ Project(_, w: Window) if (w.windowOutputSet
-- p.references).nonEmpty =>` and filter out useless window expressions
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