[GitHub] [spark] cloud-fan commented on a change in pull request #26726: [SPARK-30088][SQL]Adaptive execution should convert SortMergeJoin to BroadcastJoin when plan generates empty result

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cloud-fan commented on a change in pull request #26726: [SPARK-30088][SQL]Adaptive execution should convert SortMergeJoin to BroadcastJoin when plan generates empty result
URL: https://github.com/apache/spark/pull/26726#discussion_r353043346
 
 

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 File path: sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/QueryStageExec.scala
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 @@ -79,7 +79,9 @@ abstract class QueryStageExec extends LeafExecNode {
    */
   def computeStats(): Option[Statistics] = resultOption.map { _ =>
     // Metrics `dataSize` are available in both `ShuffleExchangeExec` and `BroadcastExchangeExec`.
-    Statistics(sizeInBytes = plan.metrics("dataSize").value)
+    // The `dataSize` metric may be a negative number when this spark plan generates empty result,
+    // since SQLMetric use -1 as initial value.
+    Statistics(sizeInBytes = Math.max(plan.metrics("dataSize").value, 0))
 
 Review comment:
   This is a bug of the `dataSize` metrics, not AQE, let's fix the underlying issue.
   
   Can you take over https://github.com/apache/spark/pull/25095 ?

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