2010YOUY01 commented on issue #16367: URL: https://github.com/apache/datafusion/issues/16367#issuecomment-2964856125
> * CPU / I/O tradeoff when `zstd` or `lz4_frame` compression is enabled i.e. compression ratio, extra latency spent for compression It's worth doing some micro-benches to see how those compressions work on Arrow arrays. We can configure several possible shapes of to-spill intermedia data (single col of different types/very wide batches/etc., perhaps just use the TPCH table), and test how different compression types perform for speed and compression ratio. It would be interesting to also test how `vortex` perform. > * Current arrow ipc stream writer always write `batch` at a time in `append_batch`. In terms of compression, it is not sure yet how much single batch can benefit from compression. This looks not so ideal, especially for compressing 'thin' batches with primitive types. If we can confirm there are huge overheads here then we should consider implementing compressing multiple batches at once. > * whether we need separate `Writer` or `Reader` implementation instead of IPC Stream Writer. > * how to introduce sort of `adaptiveness`. > > ### Describe the solution you'd like > First, we need to track (or update) how many bytes are written in spill files. Datafusion currently tracks `spilled_bytes` as part of `SpillMetrics`, but it is calculated based on in memory array size, which would be different from actual spill files size especially when we compress spill files. > > Second, update the benchmarks or write a separate benchmarks to see the performance characteristics. One possible way is writing out spill-related metrics to output.json when running benches like tpch with `debug` option. Another idea is to generate some spill files for microbenchmark testing only spill writing - reading process. 🤔 Yes now the `spilled_bytes` is not implemented correctly if compression happens, it needs a follow-up fix. Adding more micro-benchmarks sounds great. -- 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-unsubscr...@datafusion.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: github-unsubscr...@datafusion.apache.org For additional commands, e-mail: github-h...@datafusion.apache.org
