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Author: JoshRosen

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetRowConverter.scala

@@ -319,6 +319,7 @@ private[parquet] class ParquetRowConverter(
 
       case t: StructType =>
         val wrappedUpdater = {
+          // SPARK-30338: avoid unnecessary InternalRow copying for nested structs:
           if (updater.isInstanceOf[RowUpdater]) {
             // `updater` is a RowUpdater, implying that the parent container is a struct.
             // We do NOT need to perform defensive copying here because either: