pitrou opened a new issue, #47012: URL: https://github.com/apache/arrow/issues/47012
### Describe the enhancement requested When reading a Parquet leaf column as Arrow, we [presize the Arrow builder](https://github.com/apache/arrow/blob/a0cc2d8ed35dce7ee6c3e7cbcc4867216a9ef16f/cpp/src/parquet/arrow/reader.cc#L487-L488) so as to avoid spurious reallocations during incremental Parquet decoding calls. However, the `Reserve` method on `RecordReader` will [only properly reserve values](https://github.com/apache/arrow/blob/a0cc2d8ed35dce7ee6c3e7cbcc4867216a9ef16f/cpp/src/parquet/column_reader.cc#L1693-L1696) for non-FLBA non-BYTE_ARRAY physical types. The result is that, on some of our micro-benchmarks, we spend a significant amount of time reallocating data on the ArrayBuilder. ### Component(s) C++, Parquet -- 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: issues-unsubscr...@arrow.apache.org.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
