viirya commented on a change in pull request #24637: [SPARK-27707][SQL] Prune
unnecessary nested fields from Generate to address performance issue in explode
URL: https://github.com/apache/spark/pull/24637#discussion_r285965199
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -588,6 +588,16 @@ object ColumnPruning extends Rule[LogicalPlan] {
.map(_._2)
p.copy(child = g.copy(child = newChild, unrequiredChildIndex =
unrequiredIndices))
+ // prune unrequired nested fields
+ case p @ Project(projectList, g: Generate) =>
Review comment:
I think this is more general case you are looking for:
https://github.com/apache/spark/blob/163a6e298213f216f74f4764e241ee6298ea30b6/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala#L623-L624
In the general case, it's doing pruning only when the flag
(nestedSchemaPruningEnabled) is enabled. The case considers some operators that
nested project can be pushed through. `Generate` isn't one of them. So the
general case doesn't work on this case.
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