func updateHandler(ctx *fasthttp.RequestCtx) {
	n := common.GetQueriesCount(ctx)

	worlds := make([]common.World, n)
	for i := 0; i < n; i++ {
		w := &worlds[i]
		fetchRandomWorld(w)
		w.RandomNumber = int32(common.RandomWorldNum())
	}

	// sorting is required for insert deadlock prevention.
	sort.Sort(common.WorldsByID(worlds))
	txn, err := db.Begin()
	if err != nil {
		log.Fatalf("Error starting transaction: %s", err)
	}

	for i := 0; i < n; i++ {
		w := &worlds[i]
		if _, err = txn.Exec("worldUpdateStmt", w.RandomNumber, w.Id); err != nil {
			log.Fatalf("Error updating world row %d: %s", i, err)
		}
	}
	if err = txn.Commit(); err != nil {
		log.Fatalf("Error when commiting world rows: %s", err)
	}

	common.JSONMarshal(ctx, worlds)
}
func initDatabase(dbHost string, dbUser string, dbPass string, dbName string, dbPort uint16, maxConnectionsInPool int) (*pgx.ConnPool, error) {

	var successOrFailure string = "OK"

	var config pgx.ConnPoolConfig

	config.Host = dbHost
	config.User = dbUser
	config.Password = dbPass
	config.Database = dbName
	config.Port = dbPort

	config.MaxConnections = maxConnectionsInPool

	config.AfterConnect = func(conn *pgx.Conn) error {
		worldSelectStmt = mustPrepare(conn, "worldSelectStmt", "SELECT id, randomNumber FROM World WHERE id = $1")
		worldUpdateStmt = mustPrepare(conn, "worldUpdateStmt", "UPDATE World SET randomNumber = $1 WHERE id = $2")
		fortuneSelectStmt = mustPrepare(conn, "fortuneSelectStmt", "SELECT id, message FROM Fortune")
		return nil
	}

	fmt.Println("--------------------------------------------------------------------------------------------")

	connPool, err := pgx.NewConnPool(config)
	if err != nil {
		successOrFailure = "FAILED"
		log.Println("Connecting to database ", dbName, " as user ", dbUser, " ", successOrFailure, ": \n ", err)
	} else {
		log.Println("Connecting to database ", dbName, " as user ", dbUser, ": ", successOrFailure)

		log.Println("Fetching one record to test if db connection is valid...")
		var w common.World
		n := common.RandomWorldNum()
		if errPing := connPool.QueryRow("worldSelectStmt", n).Scan(&w.Id, &w.RandomNumber); errPing != nil {
			log.Fatalf("Error scanning world row: %s", errPing)
		}
		log.Println("OK")
	}

	fmt.Println("--------------------------------------------------------------------------------------------")

	return connPool, err
}
func fetchRandomWorld(w *common.World) {
	n := common.RandomWorldNum()
	if err := db.QueryRow("worldSelectStmt", n).Scan(&w.Id, &w.RandomNumber); err != nil {
		log.Fatalf("Error scanning world row: %s", err)
	}
}