type (
		Preload struct {
			ID       uint
			Value    string
			NestedID uint
		}
		Join struct {
			ID       uint
			Value    string
			NestedID uint
		}
		Nested struct {
			ID       uint
			Preloads []*Preload
			Join     Join
			ValueID  uint
		}
		Value struct {
			ID     uint
			Name   string
			Nested Nested
		}
	)

// https://www.awsarchitectureblog.com/2015/03/backoff.html
func exponentialBackoffWait(r *rand.Rand, unit, cap time.Duration) func(uint) time.Duration {
	if unit > time.Hour {
		// Protect against integer overflow
		panic("unit cannot exceed one hour")
	}
	return func(attempt uint) time.Duration {
		if attempt > 16 {
			// Protect against integer overflow
			attempt = 16
		}

			db.AddError(rows.Scan(values...))

			mapValue := map[string]interface{}{}
			scanIntoMap(mapValue, values, columns)
			*dest = append(*dest, mapValue)
		}
	case *int, *int8, *int16, *int32, *int64,
		*uint, *uint8, *uint16, *uint32, *uint64, *uintptr,
		*float32, *float64,
		*bool, *string, *time.Time,
		*sql.NullInt32, *sql.NullInt64, *sql.NullFloat64,
		*sql.NullBool, *sql.NullString, *sql.NullTime:

		// Call back.
		fn(string(key), val)
	}
	return nil
}

const (
	xlHeaderVersion = 3
	xlMetaVersion   = 2
)

type xlHeaders struct {
	versions           int
	headerVer, metaVer uint
}

func decodeXLHeaders(buf []byte) (x xlHeaders, b []byte, err error) {
	x.headerVer, buf, err = msgp.ReadUintBytes(buf)
	if err != nil {
		return x, buf, err
	}

	case float64:
		expAt, err = int64(exp), nil
	case int64:
		expAt, err = exp, nil
	case int:
		expAt, err = int64(exp), nil
	case uint64:
		expAt, err = int64(exp), nil
	case uint:
		expAt, err = int64(exp), nil
	case json.Number:
		expAt, err = exp.Int64()
	case time.Duration:
		expAt, err = time.Now().UTC().Add(exp).Unix(), nil
	case nil:
		expAt, err = 0, nil
	default:

	defer func() {
		if err := recover(); err != ErrTooLarge {
			t.Errorf("after too-large Grow, recover() = %v; want %v", err, ErrTooLarge)
		}
	}()

	buf := NewBuffer(make([]byte, 1))
	const maxInt = int(^uint(0) >> 1)
	buf.Grow(maxInt)
}

// Was a bug: used to give EOF reading empty slice at EOF.
func TestReadEmptyAtEOF(t *testing.T) {
	b := new(Buffer)
	slice := make([]byte, 0)
	n, err := b.Read(slice)