Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/11828#discussion_r56720500
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -305,21 +306,14 @@ object SetOperationPushDown extends Rule[LogicalPlan]
with PredicateHelper {
}
/**
- * Attempts to eliminate the reading of unneeded columns from the query
plan using the following
- * transformations:
- *
- * - Inserting Projections beneath the following operators:
- * - Aggregate
- * - Generate
- * - Project <- Join
- * - LeftSemiJoin
+ * Attempts to eliminate the reading of unneeded columns from the query
plan.
*/
object ColumnPruning extends Rule[LogicalPlan] {
private def sameOutput(output1: Seq[Attribute], output2:
Seq[Attribute]): Boolean =
output1.size == output2.size &&
output1.zip(output2).forall(pair => pair._1.semanticEquals(pair._2))
- def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ def apply(plan: LogicalPlan): LogicalPlan =
removeProjectBeforeFilter(plan transform {
--- End diff --
Here, we are using `transform`, which is actually `transformDown`. In this
rule `ColumnPruning`, we could add many `Project` into the child. This could
easily cause stack overflow. That is why my PR
https://github.com/apache/spark/pull/11745 is changing it to `transformUp`. Do
you think this change makes sense?
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