niyue commented on a change in pull request #11486:
URL: https://github.com/apache/arrow/pull/11486#discussion_r732845782
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File path: cpp/src/arrow/ipc/reader.cc
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@@ -1070,7 +1096,19 @@ class RecordBatchFileReaderImpl : public
RecordBatchFileReader {
read_dictionaries_ = true;
}
- ARROW_ASSIGN_OR_RAISE(auto message,
ReadMessageFromBlock(GetRecordBatchBlock(i)));
+ FieldsLoaderFunction fields_loader = {};
+ if (!field_inclusion_mask_.empty()) {
+ auto& schema = schema_;
+ auto& inclusion_mask = field_inclusion_mask_;
+ auto& read_options = options_;
+ fields_loader = [schema, inclusion_mask, read_options](
+ const flatbuf::RecordBatch* metadata,
+ io::RandomAccessFile* file) {
+ return LoadFieldsSubset(metadata, read_options, file, schema,
&inclusion_mask);
+ };
+ }
+ ARROW_ASSIGN_OR_RAISE(auto message,
+ ReadMessageFromBlock(GetRecordBatchBlock(i),
fields_loader));
Review comment:
The `fields_loader` is passed as lambda to the bottom layer (message.cc)
so that we don't have to duplicate the code of `ArrayLoader` both in
`message.cc` and `reader.cc`
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