One Billion Rows Challenge - Baseline solution in Go.

brc.go

package main

import (
	"bufio"
	"flag"
	"log/slog"
	"os"
	"strconv"
	"strings"
)

type Stat struct {
	Min   float64
	Avg   float64
	Max   float64
	Count int64
}

func computeStats(results *map[string]Stat, country string, measurement float64) {
	if stat, ok := (*results)[country]; !ok {
		(*results)[country] = Stat{measurement, measurement, measurement, 1}
	} else {
		var min float64
		if measurement < stat.Min {
			min = measurement
		} else {
			min = stat.Min
		}

		avg := (measurement - stat.Avg) / float64(stat.Count)

		var max float64
		if measurement > stat.Max {
			max = measurement
		} else {
			max = stat.Max
		}

		count := stat.Count + 1

		(*results)[country] = Stat{min, avg, max, count}
	}
}

func generateStats(path string) {
	file, err := os.Open(path)
	if err != nil {
		slog.Error(err.Error())
	}
	defer file.Close()

	scanner := bufio.NewScanner(file)

	results := make(map[string]Stat)

	for scanner.Scan() {

		splits := strings.Split(scanner.Text(), ";")

		country := splits[0]
		measurement, err := strconv.ParseFloat(splits[1], 64)
		if err != nil {
			slog.Error(err.Error())
		}

		computeStats(&results, country, measurement)

	}

	if err := scanner.Err(); err != nil {
		slog.Error(err.Error())
	}

	printStats(&results)
}

func printStats(results *map[string]Stat) {
	slog.Info("Final value", "temps", *results)
}

func main() {
	tempMeasurementsFilePath := flag.String("input", "some-requirements.txt", "Temperature measurements file.")
	flag.Parse()

	generateStats(*tempMeasurementsFilePath)
}