stdout buffering

[sstadick]

Hi! Super cool project!

I was looking at your io related code an noticed you are using std::io::stdout, which has issues: rust-lang/rust#60673

I've worked around this in other libraries of my own by using burtsushi's https://docs.rs/grep-cli/0.1.5/grep_cli/, which provides a correctly buffering stdout method when piping to a file, and line buffering when connected to a TTY.

I've seen significant speedups in my own libraries switching to buffered stdout. This may help close the single threaded gap with tsv utils.

[ezrosent]

Hey, thanks for this pointer! It does indeed look like I should be using this. To set expectations on this improving benchmarks, though, all writes are batched in a local thread and then sent to a background thread to be issued. Beyond that, the background thread uses write_all_vectored, which lets you write a whole batch without necessarily flushing after each line if I'm reading the LineBuffered implementation correctly.

Still, like I said I still think frawk should be using grep_cli; so I'll keep this open until I migrate.