Python Django迁移抛出1072键列'；汽车制造商id&x27；不'；不存在于表中

下面是简化的任务和设置（Django 1.8、MySQL、Python 2.7），我有：

class Car(models.Model):
    make = models.ForeignKey(CarMake)

class Bike(models.Model):
    make = models.ForeignKey(BikeMake)

class CarMake(models.Model):
    name = models.CharField(max_length=32)

class BikeMake(models.Model):
    name = models.CharField(max_length=32)

现在，我需要完全抛弃BikeMake模型，以便使用BikeMake中的值更新CarMake模型，并更新Bike中的外键关系

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.db import models, migrations


def update_car_makes(apps, schema_editor):
    """Update CarMakes with BikeMakes"""
    BikeMake = apps.get_model('my_app', 'BikeMake')
    CarMake = apps.get_model('my_app', 'CarMake')

    for item in BikeMake.objects.all():
        if not CarMake.objects.filter(name=item.name).exists():
            CarMake.objects.create(name=item.name)


def remove_car_makers(apps, schema_editor):
    """Restore original CarMake (exclude BikeMake)"""
    pass


def migrate_to_car_make(apps, schema_editor):
    """Set Bike.car_make according to Bike.make"""
    CarMake = apps.get_model('my_app', 'CarMake')
    Bike = apps.get_model('my_app', 'Bike')
    for item in Bike.objects.all():
        old_make = item.make
        new_make = CarMake.objects.get(name=old_make.name)
        item.car_make = new_make
        item.save()


def reverse_migrate_to_car_make(apps, schema_editor):
    pass


def dummy_forwards(apps, schema_editor):
    # Empty forward migration needed for having custom backwards migration
    pass


def restore_make_column_data(apps, schema_editor):
    BikeMake = apps.get_model('products', 'BikeMake')
    Bike = apps.get_model('products', 'Bike')

    for item in Bike.objects.all():
        old_make = item.bike_make
        new_make = BikeMake.objects.get(name=old_make.name)
        item.make = new_make
        item.save()


class Migration(migrations.Migration):

    dependencies = [('my_app', '0001_blah_blah')]

    operations = [
        migrations.RunPython(
            update_car_makers,
            reverse_code=remove_car_makers
        ),
        migrations.AddField(
            model_name='bike',
            name='car_make',
            field=models.ForeignKey(default=1, to='my_app.CarMake'),
            preserve_default=False
        ),
        migrations.RunPython(
            migrate_to_car_make,
            reverse_code=reverse_migrate_to_car_make
        ),
        migrations.RunPython(
            dummy_forwards,
            reverse_code=restore_make_column_data
        ),
        migrations.RemoveField(
            model_name='bike',
            name='make',
        ),
        migrations.RenameField(
            model_name='bike',
            old_name='car_make',
            new_name='make'
        )
    ]

我已经创建了以下迁移，它使用BikeMake中的名称更新CarMake，添加临时字段Bike.car\u make，将数据从Bike.make迁移到Bike.car\u make，删除Bike.make字段，并将Bike.car\u make重命名为Bike.make

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
from django.db import models, migrations


def update_car_makes(apps, schema_editor):
    """Update CarMakes with BikeMakes"""
    BikeMake = apps.get_model('my_app', 'BikeMake')
    CarMake = apps.get_model('my_app', 'CarMake')

    for item in BikeMake.objects.all():
        if not CarMake.objects.filter(name=item.name).exists():
            CarMake.objects.create(name=item.name)


def remove_car_makers(apps, schema_editor):
    """Restore original CarMake (exclude BikeMake)"""
    pass


def migrate_to_car_make(apps, schema_editor):
    """Set Bike.car_make according to Bike.make"""
    CarMake = apps.get_model('my_app', 'CarMake')
    Bike = apps.get_model('my_app', 'Bike')
    for item in Bike.objects.all():
        old_make = item.make
        new_make = CarMake.objects.get(name=old_make.name)
        item.car_make = new_make
        item.save()


def reverse_migrate_to_car_make(apps, schema_editor):
    pass


def dummy_forwards(apps, schema_editor):
    # Empty forward migration needed for having custom backwards migration
    pass


def restore_make_column_data(apps, schema_editor):
    BikeMake = apps.get_model('products', 'BikeMake')
    Bike = apps.get_model('products', 'Bike')

    for item in Bike.objects.all():
        old_make = item.bike_make
        new_make = BikeMake.objects.get(name=old_make.name)
        item.make = new_make
        item.save()


class Migration(migrations.Migration):

    dependencies = [('my_app', '0001_blah_blah')]

    operations = [
        migrations.RunPython(
            update_car_makers,
            reverse_code=remove_car_makers
        ),
        migrations.AddField(
            model_name='bike',
            name='car_make',
            field=models.ForeignKey(default=1, to='my_app.CarMake'),
            preserve_default=False
        ),
        migrations.RunPython(
            migrate_to_car_make,
            reverse_code=reverse_migrate_to_car_make
        ),
        migrations.RunPython(
            dummy_forwards,
            reverse_code=restore_make_column_data
        ),
        migrations.RemoveField(
            model_name='bike',
            name='make',
        ),
        migrations.RenameField(
            model_name='bike',
            old_name='car_make',
            new_name='make'
        )
    ]

当我尝试运行它时，我在运行上一个操作时得到了#1072错误：

migrations.RenameField

。现在有趣的是，从DBPOV开始，一切都已完成，数据已迁移，列已重命名，只有迁移未标记为已完成，并引发错误

另外，如果我只是将

migrations.RenameField

移动到一个单独的迁移文件中，并连续运行两次迁移，则一切正常，不会引发#1072错误

此外，我尝试在

迁移之前插入一个断点。重命名字段

，并验证了Bike.car\u make列存在，并且我可以在该点正常获取Bike模型的所有对象

导致错误的MySQL查询如下：

CREATE INDEX `my_app_bike_c2036163` ON `my_app_bike` (`car_make_id`)

有没有办法修复它并将其放在一个迁移文件中？提前谢谢

更新04.02.16

正如@kvikshaug所指出的，之所以会出现这种情况，是因为Django在执行所有操作后创建了索引和约束，即在生成用于创建索引和/或约束的原始SQL时，会执行相应的操作（在我的例子中是

AddField

），但该查询实际上是在最后运行的，因此会出现错误

对于相对较小的模式，一个可能的解决方案是使用Django并自己键入原始查询，但这相当麻烦，而且您必须自己创建约束

---

因此，我开始分离重命名迁移。

Django迁移在执行所有操作后创建索引。第二个操作是添加字段

car\u make

，使Django添加

CREATE INDEX

命令，您注意到该命令会导致错误：

CREATE INDEX `my_app_bike_c2036163` ON `my_app_bike` (`car_make_id`)

即使您后来重命名了该字段，Django仍然尝试为现在缺少的

car\u make

字段创建索引，这就是为什么会出现错误。运行

sqlmigrate

可以清楚地看到这一点：

$ ./manage.py sqlmigrate my_app 0002_blah_blah
BEGIN;
--
-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE WRITTEN AS SQL:
-- Raw Python operation
--
--
-- Add field car_make to bike
--
ALTER TABLE "my_app_bike" ADD COLUMN "car_make_id" integer DEFAULT 1 NOT NULL;
ALTER TABLE "my_app_bike" ALTER COLUMN "car_make_id" DROP DEFAULT;
--
-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE WRITTEN AS SQL:
-- Raw Python operation
--
--
-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE WRITTEN AS SQL:
-- Raw Python operation
--
--
-- Remove field make from bike
--
ALTER TABLE "my_app_bike" DROP CONSTRAINT "my_app_bike_make_id_5615ed11_fk_my_app_bikemake_id";
ALTER TABLE "my_app_bike" DROP COLUMN "make_id" CASCADE;
--
-- Rename field car_make on bike to make
--
ALTER TABLE "my_app_bike" RENAME COLUMN "car_make_id" TO "make_id";
CREATE INDEX "my_app_bike_78e8ca60" ON "my_app_bike" ("car_make_id");
ALTER TABLE "my_app_bike" ADD CONSTRAINT "my_app_bike_car_make_id_6c42be09_fk_my_app_carmake_id" FOREIGN KEY ("car_make_id") REFERENCES "my_app_carmake" ("id") DEFERRABLE INITIALLY DEFERRED;

COMMIT;

---

您可以尝试将此报告为bug（或搜索；可能已经报告），但您最好按照Alasdair的建议，将迁移分开。

我认为您可能试图在一次迁移中做太多的工作。我认为您可以进行多次迁移，例如1。创建新字段

car\u make

。2.填充

car\u make

字段。3.删除旧的

make

字段4。将

car\u make

字段重命名为

make

。可能是这样，但即使我最终将这些操作分离为几个迁移，我仍然想知道，为什么会出现错误。