cloud-fan commented on a change in pull request #33310:
URL: https://github.com/apache/spark/pull/33310#discussion_r673151153
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File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/ShuffledRowRDD.scala
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@@ -58,6 +58,12 @@ case class PartialMapperPartitionSpec(
startReducerIndex: Int,
endReducerIndex: Int) extends ShufflePartitionSpec
+// Follow-up: consider using map location for coalescing mappers
Review comment:
This is different from what I asked, but seems more reasonable. It
should be better to read the entire mapper in one task if we need small
parallelism, to avoid network data transfer. Except for location, we should
also consider the shuffle block size.
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