bolthelper.go
func (tx *Tx) WriteTo(w io.Writer) (int64, error) {
	n, err := tx.Tx.WriteTo(w)
	return n, errorsp.WithStacks(err)
}
func (tx *Tx) WriteTo(w io.Writer) (int64, error) {
	n, err := tx.Tx.WriteTo(w)
	return n, errorsp.WithStacks(err)
}
// WriteTo writes the entire database to a writer. If err == nil then
// exactly tx.Size() bytes will be written into the writer.