如果我在模型字段上更改空值和空值，是否需要进行迁移？

I have the following model

我有以下型号

@python_2_unicode_compatible
class Booking(models.Model):
    session = models.ForeignKey(verbose_name=_('Session'), to=Session, default=None, null=False, blank=False)
    quantity = models.PositiveIntegerField(verbose_name=_('Quantity'), default=1, null=False, blank=False)
    price = models.DecimalField(verbose_name=_('Price'), max_digits=10, decimal_places=2,
                                default=None, null=False, blank=False)
    name = models.CharField(verbose_name=_('Name'), max_length=100, default=None, null=False, blank=False)
    email = models.EmailField(verbose_name=_('Email'), default=None, null=True, blank=True)
    phone_number = models.CharField(verbose_name=_('Phone Number'), max_length=30, default=None, null=True, blank=True)
@python_2