[GitHub] [arrow] jorisvandenbossche commented on a change in pull request #7704: ARROW-9297: [C++][Parquet] Support chunked row groups in RowGroupRecordBatchReader

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

jorisvandenbossche commented on a change in pull request #7704:
URL: https://github.com/apache/arrow/pull/7704#discussion_r453580484



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File path: cpp/src/parquet/arrow/reader.cc
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@@ -780,11 +741,29 @@ Status GetReader(const SchemaField& field, const std::shared_ptr<ReaderContext>&
 Status FileReaderImpl::GetRecordBatchReader(const std::vector<int>& row_group_indices,
                                             const std::vector<int>& column_indices,
                                             std::unique_ptr<RecordBatchReader>* out) {
-  // column indices check
-  for (auto row_group_index : row_group_indices) {
+  // row group indices check
+  for (int row_group_index : row_group_indices) {
     RETURN_NOT_OK(BoundsCheckRowGroup(row_group_index));
   }
 
+  // column indices check
+  ARROW_ASSIGN_OR_RAISE(std::vector<int> field_indices,
+                        manifest_.GetFieldIndices(column_indices));
+
+  std::shared_ptr<::arrow::Schema> batch_schema;
+  RETURN_NOT_OK(GetSchema(&batch_schema));
+
+  // filter to only arrow::Fields which contain the selected physical columns
+  {
+    ::arrow::FieldVector selected_fields;
+
+    for (int field_idx : field_indices) {
+      selected_fields.push_back(batch_schema->field(field_idx));
+    }
+
+    batch_schema = ::arrow::schema(std::move(selected_fields));

Review comment:
       should this preserver the metadata of the original `batch_schema`? (I don't know where the `batch_schema` is further used, though)




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