[GitHub] [arrow] jorisvandenbossche commented on a change in pull request #7608: ARROW-9288: [C++][Dataset] Fix PartitioningFactory with dictionary encoding for HivePartioning

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

jorisvandenbossche commented on a change in pull request #7608:
URL: https://github.com/apache/arrow/pull/7608#discussion_r448438477



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File path: cpp/src/arrow/dataset/partition.cc
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@@ -646,15 +657,26 @@ class HivePartitioningFactory : public PartitioningFactory {
       }
     }
 
-    return impl.Finish(&dictionaries_);
+    auto schema_result = impl.Finish(&dictionaries_);
+    field_names_ = impl.FieldNames();
+    return schema_result;
   }
 
   Result<std::shared_ptr<Partitioning>> Finish(
       const std::shared_ptr<Schema>& schema) const override {
-    return std::shared_ptr<Partitioning>(new HivePartitioning(schema, dictionaries_));
+    for (FieldRef ref : field_names_) {

Review comment:
       I should probably guard here against the case that `field_names_` was not yet updated (if `Finish` is called without `Inspect` being called), with empty vector?




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