sunchao commented on a change in pull request #35657:
URL: https://github.com/apache/spark/pull/35657#discussion_r828271471



##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/execution/exchange/EnsureRequirements.scala
##########
@@ -137,8 +138,16 @@ case class EnsureRequirements(
         Some(finalCandidateSpecs.values.maxBy(_.numPartitions))
       }
 
+      // Check if 1) all children are of `DataSourcePartitioning` and 2) they 
are all compatible
+      // with each other. If both are true, skip shuffle.
+      val allCompatible = childrenIndexes.sliding(2).map {
+            case Seq(a, b) =>
+              checkDataSourceSpec(specs(a)) && checkDataSourceSpec(specs(b)) &&
+                  specs(a).isCompatibleWith(specs(b))
+          }.forall(_ == true)
+
       children = children.zip(requiredChildDistributions).zipWithIndex.map {
-        case ((child, _), idx) if !childrenIndexes.contains(idx) =>
+        case ((child, _), idx) if allCompatible || 
!childrenIndexes.contains(idx) =>

Review comment:
       `DataSourceShuffleSpec` (without enabling it to re-shuffle other 
children) can't fit nicely into this framework at the moment, I think.
   
    Since its `canCreatePartitioning` is false, we'll treat it the same as 
`RangeShuffleSpec`. In case both sides are of `DataSourceShuffleSpec`, the 
`bestSpecOpt` will be `None` in `EnsureRequirements` and Spark will create 
default partitioning from the required distribution instead.




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