package main

import (
	"database/sql"
	"flag"
	"log"
	"os"
	"runtime/pprof"
	"time"

	_ "github.com/lib/pq"
)

func main() {
	nPtr := flag.Int("n", 10, "number of goroutines")
	flag.Parse()
	nGoroutines := *nPtr

	f, err := os.Create("cpuprofile")
	if err != nil {
		log.Fatal(err)
	}
	pprof.StartCPUProfile(f)
	defer pprof.StopCPUProfile()

	db, err := sql.Open("postgres", "user=postgres host=127.0.0.1 dbname=benchmark sslmode=disable")
	if err != nil {
		log.Fatal(err)
	}

	err = db.Ping()
	if err != nil {
		log.Fatal(err)
	}
	defer db.Close()

	done := make(chan bool)

	for i := 0; i < nGoroutines; i++ {
		go func() {
			start := time.Now()
			read(db)
			log.Println(time.Since(start))
			done <- true
		}()
	}

	for i := 0; i < nGoroutines; i++ {
		<-done
	}
}

func read(db *sql.DB) {
	rows, err := db.Query("SELECT email FROM users")
	if err != nil {
		log.Fatal(err)
	}
	defer rows.Close()

	// Do nothing but iteration
	for rows.Next() {
	}
}