Strings vs. bytes

gc.go

// main.go
package main

import (
	"bytes"
	"fmt"
	"strings"
)

func main() {
	q := writeQuery()
	s := writeQueryBytes()

	fmt.Println(q, s)
}

func writeQuery() string {
	s := fmt.Sprintf("%s", strings.Join([]string{"hello", "there"}, ", "))
	v := fmt.Sprintf("%s %s", s, strings.Join([]string{"well", "some"}, ", "))
	return fmt.Sprintf("%s %s", v, strings.Join([]string{"more", "stuff"}, ", "))
}

func writeQueryBytes() string {
	buf := &bytes.Buffer{}
	args := []string{"hello", "there", "well", "some", "more", "stuff"}

	for i := 0; i < len(args); i++ {
		buf.WriteString(args[i])
		if i+1 != len(args) {
			buf.WriteString(", ")
		}
	}

	return buf.String()
}

// main_test.go
package main

import "testing"

func BenchmarkStringAlloc(b *testing.B) {
	for i := 0; i < b.N; i++ {
		writeQuery()
	}
}

func BenchmarkBytesAlloc(b *testing.B) {
	for i := 0; i < b.N; i++ {
		writeQueryBytes()
	}
}

// 🍎 scratch → gt -bench='.' -benchmem
goos: darwin
goarch: amd64
BenchmarkStringAlloc-8   	 3000000	       469 ns/op	     224 B/op	      11 allocs/op
BenchmarkBytesAlloc-8    	20000000	       104 ns/op	     112 B/op	       2 allocs/op

// 🍎 scratch → go build -gcflags='-m -l' main.go
./main.go:17:37: strings.Join([]string literal, ", ") escapes to heap
./main.go:18:19: s escapes to heap
./main.go:18:43: strings.Join([]string literal, ", ") escapes to heap
./main.go:19:21: v escapes to heap
./main.go:19:45: strings.Join([]string literal, ", ") escapes to heap
./main.go:23:9: writeQueryBytes &bytes.Buffer literal does not escape
./main.go:24:18: writeQueryBytes []string literal does not escape