timsaucer opened a new issue, #7448: URL: https://github.com/apache/arrow-rs/issues/7448
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.** The ordering of metadata is not consistent since it uses a HashMap. It can be useful in unit tests to verify an output from a known hash of it's serialized values. With metadata this is not consistent. **Describe the solution you'd like** https://github.com/apache/arrow-rs/pull/7437 **Describe alternatives you've considered** We could switch from HashMap to another map implementation or make the HashMap generic so the user could provide the hash function. I believe the solution in the PR above is a better approach. **Additional context** Here is a minimal reproducible example. If you run it multiple times you will get different output. ```rust use std::{hash::Hasher, sync::Arc}; use arrow::{array::RecordBatch, datatypes::Schema}; fn main() { let schema = Arc::new( Schema::empty().with_metadata( [ ("a".to_owned(), "1".to_owned()), // ("b".to_owned(), "2".to_owned()), // ("c".to_owned(), "3".to_owned()), // ("d".to_owned(), "4".to_owned()), // ("e".to_owned(), "5".to_owned()), // ] .into_iter() .collect(), ), ); let batch = RecordBatch::new_empty(schema.clone()); dbg!(&batch.schema().metadata().keys()); let mut bytes = Vec::new(); let mut w = arrow::ipc::writer::StreamWriter::try_new(&mut bytes, &schema).unwrap(); w.write(&batch).unwrap(); w.finish().unwrap(); let mut h = std::hash::DefaultHasher::new(); h.write(&bytes); let h = h.finish(); eprintln!("{} bytes -- h = {h:x}", bytes.len()); } ``` -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
