wangyum commented on a change in pull request #31691:
URL: https://github.com/apache/spark/pull/31691#discussion_r585180044
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
##########
@@ -613,6 +613,15 @@ object LimitPushDown extends Rule[LogicalPlan] {
case _ => join
}
LocalLimit(exp, newJoin)
+
+ case LocalLimit(limitExpr @ IntegerLiteral(limitVal),
+ window @ Window(Seq(Alias(WindowExpression(_: RankLike | _: RowNumber,
+ WindowSpecDefinition(Nil, orderSpec,
+ SpecifiedWindowFrame(RowFrame, UnboundedPreceding,
CurrentRow))), _)), _, _, child))
+ if child.maxRows.forall( _ > limitVal) =>
+ LocalLimit(
Review comment:
It should be optimized by `EliminateLimits` later. Otherwise, the plan
cannot be further optimized. Like this:
```
!GlobalLimit 2
!+- Window [row_number() windowspecdefinition(c#0 DESC NULLS LAST,
specifiedwindowframe(RowFrame, unboundedpreceding$(), currentrow$())) AS rn#0],
[c#0 DESC NULLS LAST]
! +- GlobalLimit 2
! +- LocalLimit 2
! +- Sort [c#0 DESC NULLS LAST], true
! +- LocalRelation [a#0, b#0, c#0]
```
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