mgaido91 commented on a change in pull request #25204:
[SPARK-28441][SQL][Python] Fix error when non-foldable expression is used in
correlated scalar subquery
URL: https://github.com/apache/spark/pull/25204#discussion_r307201213
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -650,7 +650,9 @@ object ColumnPruning extends Rule[LogicalPlan] {
*/
private def removeProjectBeforeFilter(plan: LogicalPlan): LogicalPlan = plan
transformUp {
case p1 @ Project(_, f @ Filter(_, p2 @ Project(_, child)))
- if p2.outputSet.subsetOf(child.outputSet) =>
+ if p2.outputSet.subsetOf(child.outputSet) &&
+ // We only remove attribute-only project.
+ p2.projectList.forall(_.isInstanceOf[AttributeReference]) =>
Review comment:
Mmmmh... I may be missing something, but I'd imagine a case like this:
```
select a, b from
(select a, b, very_expensive_operation as c from ... where a = 1)
```
Before this change, would be optimized as:
```
select a, b from
(select a, b from ... where a = 1)
```
while after it is not. Am I wrong?
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