以下的答案是基于此答案(https://stackoverflow.com/a/44148102/4129587)
为了实现它,必须执行手动数据迁移
以下5个基本的迁移步骤导致所希望的结果:
- 创建新模式
TypingResult
- 创建一个新的外键可为空的新模式
TypingResult
在旧模式TextResult
- 所有旧的属性复制到新的模式
TypingResult
- 删除旧的属性,包括从最初的模型
- 的ID改变外键为新的主键
的新实例使用新模型的自动生成迁移开始迁移可能是可能的
以下代码基于自动生成的迁移并已经过测试
from __future__ import unicode_literals
from django.conf import settings
import django.core.validators
from django.db import migrations, models
import django.db.models.deletion
def copy_text_results_to_typing_results(apps, schema_editor):
TypingResult = apps.get_model('testapp', 'TypingResult')
TextResult = apps.get_model('testapp', 'TextResult')
for text_result in TextResult.objects.all():
copied_result = TypingResult()
copied_result.user = text_result.user
copied_result.wpm = text_result.wpm
copied_result.accuracy = text_result.accuracy
copied_result.save()
text_result.typingresult_ptr = copied_result
text_result.save()
class Migration(migrations.Migration):
dependencies = [
migrations.swappable_dependency(settings.AUTH_USER_MODEL),
('testapp', '0001_initial'),
]
operations = [
migrations.CreateModel(
name='TypingResult',
fields=[
('id', models.AutoField(auto_created=True,
primary_key=True,
serialize=False,
verbose_name='ID')),
('wpm', models.FloatField(default=0.0)),
('accuracy', models.FloatField(default=1.0)),
('user', models.ForeignKey(default=1,
on_delete=django.db.models.deletion.CASCADE,
to=settings.AUTH_USER_MODEL)),
],
),
# add the foreign key for the new inherited model,
# it is allowed to have null values since the actual values have to be
# copied first to this, it will be changed later
migrations.AddField(
model_name='textresult',
name='typingresult_ptr',
field=models.OneToOneField(blank=True, null=True, to='testapp.TypingResult'),
),
# copy the old values to the new inherited model
migrations.RunPython(copy_text_results_to_typing_results),
# remove the old id and the copied fields from the TextResult model
migrations.RemoveField(
model_name='textresult',
name='accuracy',
),
migrations.RemoveField(
model_name='textresult',
name='id',
),
migrations.RemoveField(
model_name='textresult',
name='user',
),
migrations.RemoveField(
model_name='textresult',
name='wpm',
),
# alter the id of the inherited model to be the new primary key
migrations.AlterField(
model_name='textresult',
name='typingresult_ptr',
field=models.OneToOneField(auto_created=True,
on_delete=django.db.models.deletion.CASCADE,
parent_link=True,
primary_key=True,
serialize=False,
to='testapp.TypingResult'),
),
]