maropu commented on a change in pull request #29677:
URL: https://github.com/apache/spark/pull/29677#discussion_r496650338
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/EnsureRequirements.scala
##########
@@ -52,7 +52,10 @@ case class EnsureRequirements(conf: SQLConf) extends
Rule[SparkPlan] {
case (child, distribution) =>
val numPartitions = distribution.requiredNumPartitions
.getOrElse(conf.numShufflePartitions)
- ShuffleExchangeExec(distribution.createPartitioning(numPartitions),
child)
+ // Like optimizer.CollapseRepartition removes adjacent repartition
operations,
+ // adjacent repartitions performed by shuffle can be also removed.
+ val newChild = if (child.isInstanceOf[ShuffleExchangeExec])
child.children.head else child
Review comment:
> Do you mean we should check whether outputPartitioning of
ShuffleExchangeExec to be inserted and the one of the existing
ShuffleExchangeExec?
I didn't mean so; have you checked #26946? This PR currently removes
shuffles incrrectly;
```
scala> spark.range(1).selectExpr("id as a").write.saveAsTable("test")
scala> sql("SELECT /*+ REPARTITION(5) */ * FROM test ORDER BY a").explain()
== Physical Plan ==
*(2) Sort [a#5L ASC NULLS FIRST], true, 0
+- Exchange rangepartitioning(a#5L ASC NULLS FIRST, 200), true, [id=#53]
+- Exchange RoundRobinPartitioning(5), false, [id=#52] <--- !!! Removed?
!!!
+- *(1) ColumnarToRow
+- FileScan parquet default.test[a#5L] Batched: true, DataFilters:
[], Format: Parquet, Location:
InMemoryFileIndex[file:/Users/maropu/Repositories/spark/spark-master/spark-warehouse/test],
PartitionFilters: [], PushedFilters: [], ReadSchema: struct<a:bigint>
```
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