[GitHub] [iceberg] autumnust commented on a diff in pull request #6327: ORC: Fix error when projecting nested indentity partition column

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

autumnust commented on code in PR #6327:
URL: https://github.com/apache/iceberg/pull/6327#discussion_r1042526245


##########
orc/src/main/java/org/apache/iceberg/orc/ORCSchemaUtil.java:
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@@ -442,4 +445,23 @@ static TypeDescription applyNameMapping(TypeDescription orcSchema, NameMapping n
   public static Map<Integer, String> idToOrcName(Schema schema) {
     return TypeUtil.visit(schema, new IdToOrcName());
   }
+
+  /**
+   * Returns a {@link Schema} which has constant fields and metadata fields removed from the
+   * provided schema. This utility can be used to create a "read schema" which can be passed to the
+   * ORC file reader and hence avoiding deserialization and memory costs associated with column
+   * values already available through Iceberg metadata.
+   *
+   * <p>NOTE: This method, unlike {@link TypeUtil#selectNot(Schema, Set)}, preserves empty structs
+   * (caused due to a struct having all constant fields) so that Iceberg ORC readers can later add
+   * constant fields in these structs

Review Comment:
   nit: Doesn't have to mention the cause for empty structs as there might be other scenarios like intentional empty struct as part of schema ? 



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