SQLアンチパターン for Django 2章 ナイーブツリー（素朴な木）

bad-models.py

"""悪い例"""
from django.conf import settings
from django.db import models


class Bug(models.Model):
    pass


class Comment(models.Model):
    parent = models.ForeignKey(to='chapter2.Comment', on_delete=models.CASCADE)
    bug = models.ForeignKey(to=Bug, on_delete=models.CASCADE)
    author = models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.PROTECT)
    comment_date = models.DateTimeField(auto_now_add=True)
    comment_text = models.TextField()

good-1-models.py

"""良い例1"""
from django.conf import settings
from django.db import models


class Bug(models.Model):
    pass


class Comment(models.Model):
    bug = models.ForeignKey(to=Bug, on_delete=models.CASCADE)
    path = models.CharField(max_length=1000)
    author = models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.PROTECT)
    comment_date = models.DateTimeField(auto_now_add=True)
    comment_text = models.TextField()

good-2-models.py

"""良い例2"""
from django.conf import settings
from django.db import models


class Bug(models.Model):
    pass


class Comment(models.Model):
    bug = models.ForeignKey(to=Bug, on_delete=models.CASCADE)
    nsleft = models.PositiveIntegerField()
    nsright = models.PositiveIntegerField()
    author = models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.PROTECT)
    comment_date = models.DateTimeField(auto_now_add=True)
    comment_text = models.TextField()

good-3-models.py

"""良い例3"""
from django.conf import settings
from django.db import models


class Bug(models.Model):
    pass


class Comment(models.Model):
    bug = models.ForeignKey(to=Bug, on_delete=models.CASCADE)
    author = models.ForeignKey(to=settings.AUTH_USER_MODEL, on_delete=models.PROTECT)
    comment_date = models.DateTimeField(auto_now_add=True)
    comment_text = models.TextField()


class TreePath(models.Model):
    ancestor = models.ForeignKey(
        to=Comment,
        on_delete=models.CASCADE,
        related_name='ancestor',
    )
    descendant = models.ForeignKey(
        to=Comment,
        on_delete=models.CASCADE,
        related_name='descendant',
    )

    class Meta:
        unique_together = [
            ['ancestor', 'descendant'],
        ]