python - 恢复自动生成的迁移以重命名 Django 中的表时出错

Question

我在还原包含表重命名的 Django (1.8.7) 迁移时遇到问题。即使它似乎能够在 Postgres 中重命名它，它也会尝试使用旧表名添加约束。

这是回溯:

    cursor.execute(sql, params)
  File "/Users/myworkspace/projects/xxx/venv/lib/python3.5/site-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/myworkspace/projects/xxx/venv/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/Users/myworkspace/projects/xxx/venv/lib/python3.5/site-packages/django/db/utils.py", line 97, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/Users/myworkspace/projects/xxx/venv/lib/python3.5/site-packages/django/utils/six.py", line 658, in reraise
    raise value.with_traceback(tb)
  File "/Users/myworkspace/projects/xxx/venv/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: relation "team_membershiprole" does not exist

如果您看一下它生成的 SQL，

[...]
ALTER TABLE "team_membershiprole" RENAME TO "team_leadershiprole";
[...]
ALTER TABLE "team_leadershipteammember" 
    ADD CONSTRAINT "team_l_role_id_xxx" 
    FOREIGN KEY ("role_id") REFERENCES "team_membershiprole" ("id")     
    DEFERRABLE INITIALLY DEFERRED;
[...]

COMMIT;

您可以看到有对 team_membershiprole 的引用，即使该表已不存在(已重命名)。这是迁移代码:

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import models, migrations


class Migration(migrations.Migration):

    dependencies = [
        ('core', '0023_xxx'),
        ('team', '0009_xxx2'),
    ]

    operations = [
        migrations.CreateModel(
            name='TeamMembership',
            fields=[
                ('id', models.AutoField(serialize=False, auto_created=True, verbose_name='ID', primary_key=True)),
                ('team', models.ForeignKey(related_name='members', to='team.Team')),
                ('member', models.ForeignKey(to='core.Member')),
            ],
        ),
        migrations.RenameModel(
            old_name='LeadershipRole',
            new_name='MembershipRole',
        ),
        migrations.RemoveField(
            model_name='leadershipteammember',
            name='team',
        ),
        migrations.RemoveField(
            model_name='leadershipteammember',
            name='member',
        ),
        migrations.RemoveField(
            model_name='leadershipteammember',
            name='role',
        ),
        migrations.DeleteModel(
            name='LeadershipTeamMember',
        ),
        migrations.AddField(
            model_name='teammembership',
            name='role',
            field=models.ForeignKey(to='team.MembershipRole'),
        ),
    ]

我知道这可能是一个 Django 迁移错误，但是有什么办法可以解决这个问题吗？

Answer 1

您可以覆盖 Migration.unapply，以便它使用一组不同的操作。

class MyMigration(Migration):
    operations = [
        ... your operations ...
    ]
    reverse_operations = [
        ... your fixed reverse operations ...
    ]
    def unapply(self, project_state, schema_editor, collect_sql=False):
        self.operations = self.reverse_operations
        return super(MyMigration, self).unapply(..)

我还没有测试过这个，但它应该会给你一个想法。哦，你可能需要反转反向迁移列表，因为 Django 会期望它是正向迁移列表，所以反向遍历它们。