Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/10454#discussion_r48392176
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
---
@@ -858,6 +859,30 @@ object PushPredicateThroughJoin extends
Rule[LogicalPlan] with PredicateHelper {
}
/**
+ * Push [[Limit]] operators through [[Join]] operators, iff the join type
is outer joins.
+ * Adding extra [[Limit]] operators on top of the outer-side
child/children.
+ */
+object PushLimitThroughOuterJoin extends Rule[LogicalPlan] with
PredicateHelper {
+
+ def apply(plan: LogicalPlan): LogicalPlan = plan transform {
+ case f @ Limit(expr, Join(left, right, joinType, joinCondition)) =>
+ joinType match {
+ case RightOuter =>
+ Limit(expr, Join(left, CombineLimits(Limit(expr, right)),
joinType, joinCondition))
--- End diff --
Since we call `CombineLimits` here to combine two consecutive `Limit`s, we
will not add extra `Limit` in the subsequent iteration. Thus, no change will be
made in the plan. Thus, `RuleExecutor` will stop automatically. Am I right?
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