在Django模型中，唯一的时间戳如何在违反约束时递增？

from django.db import models

class MyModel(models.Model):
    id = models.AutoField(primary_key=True)
    timestamp = models.DateTimeField(auto_now_add=True)

from django.db import models

class MyModel(models.Model):
    id = models.AutoField(primary_key=True)
    timestamp = models.DateTimeField(auto_now=True)

from django.db import models

class MyModel(models.Model):
    id = models.AutoField(primary_key=True)
    timestamp = models.DateTimeField(auto_now=True)
    other_field = models.CharField(max_length=100)

    class Meta:
        unique_together = ('timestamp', 'other_field')