[GitHub] [spark] dongjoon-hyun commented on a change in pull request #23867: [SPARK-26965][SQL] Makes ElementAt nullability more precise

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dongjoon-hyun commented on a change in pull request #23867: [SPARK-26965][SQL] Makes ElementAt nullability more precise
URL: https://github.com/apache/spark/pull/23867#discussion_r261899066
 
 

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 File path: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
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 @@ -1974,7 +1975,10 @@ case class ElementAt(left: Expression, right: Expression) extends GetMapValueUti
     }
   }
 
-  override def nullable: Boolean = true
+  override def nullable: Boolean = left.dataType match {
+    case _: ArrayType => computeNullabilityFromArray(left, right)
+    case _: MapType => computeNullabilityFromMap
 
 Review comment:
   If `Map` is out of the scope, shall we update the title and use the following code path instead?
   - Remove `extends GetMapValueUtil`.
   - Remove `computeNullabilityFromMap` and use the following.
    ```scala
   case _: MapType => true
   ```

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