cloud-fan commented on code in PR #37612:
URL: https://github.com/apache/spark/pull/37612#discussion_r954560331
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sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/AQEUtils.scala:
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@@ -28,16 +28,31 @@ object AQEUtils {
def getRequiredDistribution(p: SparkPlan): Option[Distribution] = p match {
// User-specified repartition is only effective when it's the root node,
or under
// Project/Filter/LocalSort/CollectMetrics.
- // Note: we only care about `HashPartitioning` as `EnsureRequirements` can
only optimize out
- // user-specified repartition with `HashPartitioning`.
- case ShuffleExchangeExec(h: HashPartitioning, _, shuffleOrigin)
+ // Note, here are two cases of how user-specified repartition can be
optimized out:
+ // 1. `EnsureRequirements` can only optimize out user-specified
repartition with
+ // `HashPartitioning`.
+ // 2. `AQEOptimizer` can optimize out user-specified repartition with all
`Partitioning`,
+ // e.g. convert empty to local relation.
Review Comment:
OK let me make my proposal clear: let's not optimize out repartition if it's
the root node, or below Project/Filter, in any cases. What do you think?
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