[GitHub] [arrow] pitrou commented on issue #34509: [C++][Parquet] batch size in ArrowReaderProperties does not affect ReadTable API

["pitrou (via GitHub)" <gi...@apache.org>]

pitrou commented on issue #34509:
URL: https://github.com/apache/arrow/issues/34509#issuecomment-1623615380

   The silly thing is that `FileReaderImpl::GetRecordBatchGenerator` seems to read one table per row group and then slices that table in batch-size'd record batches. @lidavidm Do you remember why is that?
   ```c++
       const int64_t batch_size = self->properties().batch_size();
       return self->DecodeRowGroups(self, {row_group}, column_indices, cpu_executor)
           .Then([batch_size](const std::shared_ptr<Table>& table)
                     -> ::arrow::Result<RecordBatchGenerator> {
             ::arrow::TableBatchReader table_reader(*table);
             table_reader.set_chunksize(batch_size);
             ARROW_ASSIGN_OR_RAISE(auto batches, table_reader.ToRecordBatches());
             return ::arrow::MakeVectorGenerator(std::move(batches));
           });
   ```


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: github-unsubscribe@arrow.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org