[GitHub] [arrow] pitrou commented on a change in pull request #8366: ARROW-9943: [C++] Recursively apply Arrow metadata when reading from Parquet

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

pitrou commented on a change in pull request #8366:
URL: https://github.com/apache/arrow/pull/8366#discussion_r500443163



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File path: cpp/src/parquet/arrow/schema.cc
##########
@@ -689,10 +686,91 @@ Status GetOriginSchema(const std::shared_ptr<const KeyValueMetadata>& metadata,
 // but that is not necessarily present in the field reconstitued from Parquet data
 // (for example, Parquet timestamp types doesn't carry timezone information).
 
-Status ApplyOriginalStorageMetadata(const Field& origin_field, SchemaField* inferred) {
+Result<bool> ApplyOriginalMetadata(const Field& origin_field, SchemaField* inferred);
+
+using NestedFieldRewrapper = std::function<Status(FieldVector, SchemaField*)>;
+
+Status RewrapStructField(FieldVector new_children, SchemaField* inferred) {
+  inferred->field = inferred->field->WithType(::arrow::struct_(std::move(new_children)));
+  return Status::OK();
+}
+
+Status RewrapListField(FieldVector new_children, SchemaField* inferred) {
+  DCHECK_EQ(new_children.size(), 1);
+  inferred->field = inferred->field->WithType(::arrow::list(new_children[0]));
+  return Status::OK();
+}
+
+NestedFieldRewrapper GetNestedFieldRewrapper(const ArrowType& origin_type,
+                                             const ArrowType& inferred_type) {
+  switch (inferred_type.id()) {
+    case ::arrow::Type::STRUCT:
+      if (origin_type.id() == ::arrow::Type::STRUCT) {
+        return RewrapStructField;
+      }
+      break;
+    case ::arrow::Type::LIST:
+      // TODO also allow LARGE_LIST and FIXED_SIZE_LIST

Review comment:
       @emkornfield I think you'll be able to add your changes here.




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