beliefer commented on code in PR #36541:
URL: https://github.com/apache/spark/pull/36541#discussion_r873406676
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sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala:
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@@ -81,55 +81,56 @@ abstract class SparkStrategies extends
QueryPlanner[SparkPlan] {
*/
object SpecialLimits extends Strategy {
override def apply(plan: LogicalPlan): Seq[SparkPlan] = plan match {
- case ReturnAnswer(rootPlan) => rootPlan match {
- case Limit(IntegerLiteral(limit), Sort(order, true, child))
- if limit < conf.topKSortFallbackThreshold =>
- TakeOrderedAndProjectExec(limit, order, child.output,
planLater(child)) :: Nil
- case Limit(IntegerLiteral(limit), Project(projectList, Sort(order,
true, child)))
- if limit < conf.topKSortFallbackThreshold =>
- TakeOrderedAndProjectExec(limit, order, projectList,
planLater(child)) :: Nil
+ // Call `planTakeOrdered` first which matches a larger plan.
+ case ReturnAnswer(rootPlan) =>
planTakeOrdered(rootPlan).getOrElse(rootPlan match {
+ // We should match the combination of limit and offset first, to get
the optimal physical
+ // plan, instead of planning limit and offset separately.
+ case LimitAndOffset(limit, offset, child) =>
+ CollectLimitExec(limit = limit, child = planLater(child), offset =
offset)
+ case OffsetAndLimit(offset, limit, child) =>
+ // 'Offset a' then 'Limit b' is the same as 'Limit a + b' then
'Offset a'.
+ CollectLimitExec(limit = offset + limit, child = planLater(child),
offset = offset)
Review Comment:
ditto
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