Remove automatic buffering in ipc::reader::FileReader for for consistent buffering
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Current writer API automatically wraps the supplied std::io::Writer impl into a BufWriter. It is cleaner and more idiomatic to have the default be using the supplied impl directly, as the user might already have a BufWriter or an impl that doesn't actually benefit from buffering at all. StreamReader does a similar thing, but it also exposes a `try_new_unbuffered` that bypasses the internal wrap. Here we propose a consistent and non-buffered by default API: - `try_new` does not wrap the passed reader/writer, - `try_new_buffered` is a convenience function that does wrap the reader/writer into a BufReader/BufWriter, - all four publicly exposed IPC reader/writers follow the above consistently, i.e. `StreamReader`, `FileReader`, `StreamWriter`, `FileWriter`. Those are breaking changes. An additional tweak: removed the generic type bounds from struct definitions on the four types, as that is the idiomatic Rust approach (see e.g. stdlib's HashMap that has no bounds on the struct definition, only the impl requires Hash + Eq). See apache#6099 for the discussion.
Applied a few suggestions, made `Error` sections more consistent.
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ipc::reader::FileReader for for consistent buffering
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Which issue does this PR close?
Closes #6099.
Rationale for this change
Current writer API automatically wraps the supplied
std::io::Writerimpl into aBufWriter.It is cleaner and more idiomatic to have the default be using the supplied impl directly, as the user might already have a
BufWriteror an impl that doesn't actually benefit from buffering at all.StreamReader does a similar thing, but it also exposes a
try_new_unbufferedthat bypasses the internal wrap. These APIs are incosistent between reader/writer and also betweenStreamandFileversions, but there's no strong reason for that.What changes are included in this PR?
Here we propose a consistent and non-buffered by default API:
try_newdoes not wrap the passed reader/writer,try_new_bufferedis a convenience function that does wrap the reader/writer into a BufReader/BufWriter,StreamReader,FileReader,StreamWriter,FileWriter.An additional tweak: removed the generic type bounds from struct definitions on the four types, as that is the idiomatic Rust approach (see e.g. stdlib's
HashMapthat has no bounds on the struct definition, only the impl requiresHash + Eq).Are there any user-facing changes?
arrow_ipc::reader::StreamReader<R>::try_new_unbufferedis deprecated to be removed in a future version;arrow_ipc::reader::StreamReader<std::io::BufReader<R>>::try_newis renamed totry_new_buffered;arrow_ipc::reader::FileReader<std::io:::BufReader<R>>::try_new_bufferedis added;arrow_ipc::writer::StreamWriter<std::io::BufWriter<W>>::try_new_bufferedis added;arrow_ipc::writer::FileWriter<std::io::BufWriter<W>>::try_new_bufferedis added.The fact that
try_newis now unbuffered is a silent change from the API perspective. A number of rustdocs explicitly referenced the internal buffering and have been reworded accordingly.