questions about wordcount example

I write a WordCount example with your framework as follows. It only processes a 17-lines text but takes 240s to finish on my computer. Why does it run so slow?

use chrono::prelude::*;
use vega::io::*;
use vega::*;
use std::fs::File;

fn main() -> Result<()> {
    let context = Context::new()?;

    let num_splits = 4;
    let deserializer = Fn!(|file: Vec<u8>| {
        String::from_utf8(file)
        .unwrap()
        .lines()
        .map(|s| s.to_string())
        .collect::<Vec<_>>()
    });
    let lines = context
                .read_source(LocalFsReaderConfig::new("./README.md"), deserializer)
                .flat_map(Fn!(|lines: Vec<String>| {
                    Box::new(lines.into_iter()) as Box<dyn Iterator<Item = _>>
                }));

    let words = lines.flat_map(Fn!(|line: String| {
        Box::new(line.split(' ').map(|s| (s.to_string(), 1)).collect::<Vec<_>>().into_iter()) as Box<dyn Iterator<Item = _>>
    }));

    let result = words.reduce_by_key(Fn!(|(a, b)| a + b), num_splits);

    let output = result.collect().unwrap();

    println!("result: {:?}", output);

    Ok(())
}

rajasekarv / vega

questions about wordcount example #127