maryannxue commented on a change in pull request #32816:
URL: https://github.com/apache/spark/pull/32816#discussion_r706244614
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File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/simpleCosting.scala
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@@ -35,15 +36,48 @@ case class SimpleCost(value: Long) extends Cost {
}
/**
- * A simple implementation of [[CostEvaluator]], which counts the number of
- * [[ShuffleExchangeLike]] nodes in the plan.
+ * A skew join aware implementation of [[Cost]], which consider shuffle number
and skew join number
Review comment:
Can we add more description on how the cost is calculated in the
presence of skew joins? What happens if there's two or more extra shuffles by
adding a skew join optimization?
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