[GitHub] [spark] cloud-fan commented on a diff in pull request #37207: [SPARK-39792][SQL] Add DecimalDivideWithOverflowCheck for decimal average

[GitBox <gi...@apache.org>]

cloud-fan commented on code in PR #37207:
URL: https://github.com/apache/spark/pull/37207#discussion_r922979739


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/decimalExpressions.scala:
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@@ -247,3 +247,76 @@ case class DecimalAddNoOverflowCheck(
       newLeft: Expression, newRight: Expression): DecimalAddNoOverflowCheck =
     copy(left = newLeft, right = newRight)
 }
+
+/**
+ * A divide expression for decimal values which is only used internally by Avg.
+ *
+ * It will fail when nullOnOverflow is false follows:
+ *   - left is null, as the right side should never be null

Review Comment:
   since we only invoke `DecimalDivideWithOverflowCheck` when count > 0, I think left (`sum` in AVG) will never be null?



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