如何将不同的 Db 模型合并为一个？

Question

我有一个旧的 Django 项目，我是初学者时就开始的。 到目前为止它有效，但是由于我想进行一些代码重构，我想更改原始数据库模型。 基本上，我最初做了很多不同的模型，每一个都针对一种用户类型。

旧型号：

class CustomUser(AbstractUser):
    user_type_data = (
        ('admin', 'Admin'),
        ('instructor', 'Instructor'),
        ('student', 'Student'),
        ('renter', 'Renter'),
    )
    user_type = models.CharField(
        max_length=20, choices=user_type_data, default=1)


class Admin(models.Model):
    user = models.OneToOneField(CustomUser, on_delete=models.CASCADE)
    first_name = models.CharField(max_length=200)
    last_name = models.CharField(max_length=200)
    date_of_birth = models.DateField(null=True, blank=True)
    fiscal_code = models.CharField(max_length=50, null=True, blank=True)
    phone = models.CharField(max_length=50, null=True, blank=True)
    picture = models.ImageField(
        blank=True, null=True, default='default.png')
    address = models.CharField(max_length=100, blank=True, null=True)
    cap = models.CharField(max_length=10, blank=True, null=True)
    city = models.CharField(max_length=100, blank=True, null=True)
    province = models.CharField(
        max_length=100, choices=PROVINCE_CHOICES, blank=True, null=True)
    country = CountryField(blank=True, null=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    is_active = models.BooleanField(default=True)

    def __str__(self):
        return self.user.username

    class Meta:
        ordering = ['last_name']


class Instructor(models.Model):
    user = models.OneToOneField(CustomUser, on_delete=models.CASCADE)
    first_name = models.CharField(max_length=200)
    last_name = models.CharField(max_length=200)
    date_of_birth = models.DateField(null=True, blank=True)
    fiscal_code = models.CharField(max_length=50,  null=True, blank=True)
    phone = models.CharField(max_length=50,  null=True, blank=True)
    picture = models.ImageField(
        blank=True, null=True, default='default.png')
    address = models.CharField(max_length=100, null=True, blank=True)
    cap = models.CharField(max_length=10, null=True, blank=True)
    city = models.CharField(max_length=100, null=True, blank=True)
    province = models.CharField(
        max_length=100, choices=PROVINCE_CHOICES, blank=True, null=True)
    country = CountryField(blank=True, null=True)
    is_active = models.BooleanField(default=True)
    flight_wage = models.FloatField(null=True, blank=True)
    theory_wage = models.FloatField(null=True, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.user.last_name + ' ' + self.user.first_name

    class Meta:
        ordering = ['last_name']

我只发布了前两种用户类型，但你明白了。 大量冗余代码。 我想要实现的是这样的：

新模型.py：

class CustomUser(AbstractUser):

    user_type_data = (
        ('admin', 'Admin'),
        ('instructor', 'Instructor'),
        ('student', 'Student'),
        ('renter', 'Renter'),
    )
    user_type = models.CharField(
        max_length=20, choices=user_type_data, default=1)
    first_name = models.CharField(max_length=200)
    last_name = models.CharField(max_length=200)
    date_of_birth = models.DateField(null=True, blank=True)
    fiscal_code = models.CharField(max_length=50,  null=True, blank=True)
    phone = models.CharField(max_length=50,  null=True, blank=True)
    picture = models.ImageField(
        blank=True, null=True, default='default.png')
    address = models.CharField(max_length=100, null=True, blank=True)
    cap = models.CharField(max_length=10, null=True, blank=True)
    city = models.CharField(max_length=100, null=True, blank=True)
    province = models.CharField(
        max_length=100, choices=PROVINCE_CHOICES, blank=True, null=True)
    country = CountryField(blank=True, null=True)
    is_active = models.BooleanField(default=True)
    flight_wage = models.FloatField(null=True, blank=True)
    theory_wage = models.FloatField(null=True, blank=True)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)

    def __str__(self):
        return self.user.last_name + ' ' + self.user.first_name

    class Meta:
        ordering = ['last_name']

我的问题是：是否可以将我的旧项目（我已经有两个客户在使用旧项目）适应这个新品牌类型的数据库 model？

Answer 1

我将通过以下步骤执行此操作：

1. 向现有用户 model 添加新字段，确保为所有新字段添加 null=True
2. 为用户 model 创建迁移文件
3. 在迁移文件中添加一个 migrations.RunPython 命令以将 Admin model 中的值添加到每个相应的用户。
4. 运行迁移并从所有不需要的字段中删除 null=True
5. 重构所有代码以引用用户 model 而不是管理员 model
6. 删除管理员 model

可以对 Instructor model 执行相同的操作

我将在这里给出第 3 步的示例：

## Example migration file

from django.db import migrations

def add_values_to_user(apps, schema):
    CustomUser = apps.get_model('users', 'CustomUser')

    for user in CustomUser.objects.all():
        if user.admin:
            user.first_name = user.admin.first_name
        elif user.instructor:
            user.first_name = user.instructor.first_name
        # Do this for all values you require for the admin and instructor model

        user.save()

class Migration(migrations.Migration):

    dependencies = [
        ('users', '0046_auto_20220506_1523'),
    ]

    operations = [
        migrations.RunPython(add_values_to_user)
    ]

Answer 2

也许你正在寻找的是代理模型： https://docs.djangoproject.com/en/4.1/topics/db/models/#proxy-models

来自文档： This is what proxy model inheritance is for: creating a proxy for the original model. You can create, delete and update instances of the proxy model and all the data will be saved as if you were using the original (non-proxied) model. The difference is that you can change things like the default model ordering or the default manager in the proxy, without having to alter the original.

from django.db import models

class Person(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)

class MyPerson(Person):
    class Meta:
        proxy = True

    def do_something(self):
        # ...
        pass

The MyPerson class operates on the same database table as its parent Person class. In particular, any new instances of Person will also be accessible through MyPerson, and vice-versa