[GitHub] [spark] Yaohua628 commented on a diff in pull request #40035: [SPARK-41151][FOLLOW-UP][SQL] Improve the doc of `_metadata` generated columns nullability implementation

["Yaohua628 (via GitHub)" <gi...@apache.org>]

Yaohua628 commented on code in PR #40035:
URL: https://github.com/apache/spark/pull/40035#discussion_r1107928238


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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala:
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@@ -578,6 +578,11 @@ object FileSourceGeneratedMetadataAttribute {
 
   val FILE_SOURCE_GENERATED_METADATA_COL_ATTR_KEY = "__file_source_generated_metadata_col"
 
+  // We keep generated metadata attributes nullability configurable here:
+  // 1. Before passing to readers, we create generated metadata attributes as nullable;
+  //    Because, for row_index, the readers do not consider the column required.
+  // 2. When applying the projection, we change the nullability back to not-nullable;
+  // See [[FileSourceStrategy.scala]] for more information

Review Comment:
   Thanks! Addressed



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