[GitHub] [spark] aokolnychyi commented on a change in pull request #29089: [SPARK-32276][SQL] Remove redundant sorts before repartition nodes

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aokolnychyi commented on a change in pull request #29089:
URL: https://github.com/apache/spark/pull/29089#discussion_r454024892



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
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@@ -981,6 +982,10 @@ object EliminateSorts extends Rule[LogicalPlan] {
       j.copy(left = recursiveRemoveSort(originLeft), right = recursiveRemoveSort(originRight))
     case g @ Aggregate(_, aggs, originChild) if isOrderIrrelevantAggs(aggs) =>
       g.copy(child = recursiveRemoveSort(originChild))
+    case r: RepartitionByExpression =>

Review comment:
       I am +1 on having a repartition node that preserves ordering. In fact, we have such a node internally. `Coalesce` is not really order preserving, though. It has custom logic in `DefaultPartitionCoalescer` that gets applied if the parent RDD has locality info. We would also need to report `outputOrdering` correctly (which is not done in case of `Coalesce` now)




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