[GitHub] [spark] viirya commented on a change in pull request #29587: [SPARK-32376][SQL] Make unionByName null-filling behavior work with struct columns

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viirya commented on a change in pull request #29587:
URL: https://github.com/apache/spark/pull/29587#discussion_r480237210



##########
File path: sql/catalyst/src/main/scala/org/apache/spark/sql/types/StructType.scala
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@@ -641,4 +641,30 @@ object StructType extends AbstractDataType {
     fields.foreach(s => map.put(s.name, s))
     map
   }
+
+  /**
+   * Returns a `StructType` that contains missing fields recursively from `source` to `target`.
+   * Note that this doesn't support looking into array type and map type recursively.
+   */
+  def findMissingFields(source: StructType, target: StructType, resolver: Resolver): StructType = {

Review comment:
       I feel this is more general method related to `StructType`. So putting it in `StructType`. 




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