[GitHub] [spark] viirya commented on a change in pull request #29983: [SPARK-13860][SQL] Change CentralMomentAgg to return null instead of Double.NaN when divideByZero

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viirya commented on a change in pull request #29983:
URL: https://github.com/apache/spark/pull/29983#discussion_r502868488



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File path: sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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@@ -2342,6 +2342,16 @@ object SQLConf {
       .booleanConf
       .createWithDefault(false)
 
+  val LEGACY_CENTRAL_MOMENT_AGG =
+    buildConf("spark.sql.legacy.centralMomentAgg")
+      .internal()
+      .doc("When set to true, central moment aggregation will return Double.NaN " +
+        "if divide by zero occurred during calculation. " +
+        "Otherwise, it will return null")

Review comment:
       Can we describe the Spark version of this legacy behavior? E.g., In what versions it returns NaN.




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