Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/6780#discussion_r32301095
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -107,6 +108,17 @@ object UnionPushdown extends Rule[LogicalPlan] {
}
}
+object LimitPushDown extends Rule[LogicalPlan] {
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ // Push down limit when the child is project on limit
+ case Limit(expr, Project(projectList, l: Limit)) =>
+ Project(projectList, Limit(expr, l))
+
+ // Push down limit when the child is project on sort
+ case Limit(expr, Project(projectList, s: Sort)) =>
+ Project(projectList, Limit(expr, s))
+ }
--- End diff --
This is for SPARK-7289. As we discussed in
https://github.com/apache/spark/pull/5821, we need an optimize rule like this.
cc @adrian-wang
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