Django：如何迁移到基于类的索引

Question

Django 1.11 引入了基于类的模型索引。之前定义为

class A(models.Model):
    class Meta:
        index_together = [
            ('foo', 'bar'),
        ]

现在可以定义为

class A(models.Model):
    class Meta:
        indexes = [
            models.Index(fields=['foo', 'bar']),
        ]

当我更改为模型运行的新语法时

python manage.py makemigrations

，它将创建类似

的迁移

class Migration(migrations.Migration):

    dependencies = [
        ('app', '0001_initial'),
    ]

    operations = [
        migrations.AlterIndexTogether(
            name='a',
            index_together=set([]),
        ),
        migrations.AddIndex(
            model_name='a',
            index=models.Index(fields=['foo', 'bar'], name='app_a_f12345_idx'),
        ),
    ]

此迁移将删除并重新创建我的索引，这是我想避免的事情。

从旧语法切换到新语法的推荐方法是什么？我在文档中找不到任何内容。

Answer 1

您可以编辑生成的迁移，使索引

name

与原始

index_together

索引名称匹配，然后使用

manage.py migrate

选项运行

--fake

。

Answer 2

而不是

--fake

，我想使用一些会自动应用于各种数据库的东西，仅用于此特定迁移。因此，我最终使用了

AddIndex

、

RemoveIndex

、

RenameIndex

和

SeparateDatabaseAndState

的组合，因为 Django 将我在上游修改的这个索引视为新索引。

# Generated by Django 4.2.18

from django.db import migrations


class Migration(migrations.Migration):

    dependencies = [
        ("app_name", "00XX_auto_XXXX"),
    ]

    operations = [
        # Handle this operation a bit differently since old migrations had to be updated to get rid of `index_together` references
        migrations.SeparateDatabaseAndState(
            # What actually happens
            database_operations=[
                migrations.RenameIndex(
                    model_name="model_name",
                    new_name="model_xxx_idx",
                    old_fields=("field1", "field2"),
                ),
            ],
            # What we want Django to believe happened
            state_operations=[
                migrations.RemoveIndex(
                    model_name="model_name",
                    name="model_xxx_idx_archive",
                ),
                migrations.RenameIndex(
                    model_name="model_name",
                    new_name="model_xxx_idx",
                    old_fields=("field1", "field2"),
                ),
            ],
        ),
    ]