gistfile1.txt

package main

import (
	"log"
	"math/rand"
	"strings"

	"gopkg.in/pg.v4"
)

func main() {
	db := pg.Connect(&pg.Options{
		User:     "postgres",
		PoolSize: 50,
	})

	qs := []string{
		`DROP TABLE IF EXISTS repack_issue_70`,
		`CREATE TABLE repack_issue_70 (id serial PRIMARY KEY, hash int)`,
		`CREATE UNIQUE INDEX on repack_issue_70 (hash) WHERE hash IS NOT NULL`,
	}
	for _, q := range qs {
		_, err := db.Exec(q)
		if err != nil {
			log.Fatal(err)
		}
	}

	for i := 0; i < 100; i++ {
		go thread(db)
	}

	log.Print("ready...")
	select {}
}

func thread(db *pg.DB) {
	for i := uint(0); ; i++ {
		hash := rand.Intn(100)

		_, err := db.Exec(`
			INSERT INTO repack_issue_70 (hash) VALUES (?)
		`, hash)
		if err != nil {
			if !strings.Contains(err.Error(), "duplicate key") {
				log.Fatal(err)
			}
		}

		if i%2 == 0 {
			_, err := db.Exec(`
				UPDATE repack_issue_70
				SET hash = NULL
				WHERE hash = ?
			`, hash)
			if err != nil {
				log.Fatal(err)
			}
		}
	}
}