Github user jaceklaskowski commented on a diff in the pull request:
https://github.com/apache/spark/pull/14327#discussion_r71992242
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -150,13 +150,20 @@ class SimpleTestOptimizer extends Optimizer(
/**
* Pushes projects down beneath Sample to enable column pruning with
sampling.
+ * This rule is only doable when the projects don't add new attributes.
*/
object PushProjectThroughSample extends Rule[LogicalPlan] {
def apply(plan: LogicalPlan): LogicalPlan = plan transform {
// Push down projection into sample
- case Project(projectList, Sample(lb, up, replace, seed, child)) =>
+ case p @ Project(projectList, Sample(lb, up, replace, seed, child))
+ if !hasNewOutput(projectList, p.child.output) =>
Sample(lb, up, replace, seed, Project(projectList, child))()
}
+ private def hasNewOutput(
+ projectList: Seq[NamedExpression],
+ childOutput: Seq[Attribute]): Boolean = {
+ projectList.exists(p => !childOutput.exists(_.semanticEquals(p)))
--- End diff --
It's hard to understand what the code does -- two `exists` and negation.
Can you "untangle" it?
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