Python Django ProgrammingError:在Django源代码中创建迁移后，关系是否已存在？

我最近签出了一个项目的主分支，迁移中还没有反映模型更改：

(venv) Kurts-MacBook-Pro-2:lucy-web kurtpeek$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auditlog, auth, contenttypes, lucy_web, oauth2_provider, otp_static, otp_totp, sessions, two_factor
Running migrations:
  No migrations to apply.
  Your models have changes that are not yet reflected in a migration, and so won't be applied.
  Run 'manage.py makemigrations' to make new migrations, and then re-run 'manage.py migrate' to apply them.

# -*- coding: utf-8 -*-
# Generated by Django 1.11.9 on 2018-04-25 18:29
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('auth', '0008_alter_user_username_max_length'),
    ]

    operations = [
        migrations.AlterField(
            model_name='user',
            name='email',
            field=models.EmailField(blank=True, max_length=254, unique=True, verbose_name='email address'),
        ),
    ]

按照说明，我运行了

makemigrations

来创建它们：

(venv) Kurts-MacBook-Pro-2:lucy-web kurtpeek$ python manage.py makemigrations
Migrations for 'auth':
  venv/lib/python3.6/site-packages/django/contrib/auth/migrations/0009_auto_20180425_1129.py
    - Alter field email on user
Migrations for 'lucy_web':
  lucy_web/migrations/0146_auto_20180425_1129.py
    - Alter field description on sessiontype
    - Alter field short_description on sessiontype

有趣的是，

0009_auto_20180425_1129.py

迁移是在包含Django源代码（版本1.11.9）的

venv

中创建的，我相信我们团队中没有人更改过。以下是迁移：

(venv) Kurts-MacBook-Pro-2:lucy-web kurtpeek$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auditlog, auth, contenttypes, lucy_web, oauth2_provider, otp_static, otp_totp, sessions, two_factor
Running migrations:
  No migrations to apply.
  Your models have changes that are not yet reflected in a migration, and so won't be applied.
  Run 'manage.py makemigrations' to make new migrations, and then re-run 'manage.py migrate' to apply them.

# -*- coding: utf-8 -*-
# Generated by Django 1.11.9 on 2018-04-25 18:29
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('auth', '0008_alter_user_username_max_length'),
    ]

    operations = [
        migrations.AlterField(
            model_name='user',
            name='email',
            field=models.EmailField(blank=True, max_length=254, unique=True, verbose_name='email address'),
        ),
    ]

这似乎“足够天真”，但当我尝试迁移时，我得到了以下

编程错误

：

(venv) Kurts-MacBook-Pro-2:lucy-web kurtpeek$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auditlog, auth, contenttypes, lucy_web, oauth2_provider, otp_static, otp_totp, sessions, two_factor
Running migrations:
  Applying auth.0009_auto_20180425_1129...Traceback (most recent call last):
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: relation "auth_user_email_1c89df09_uniq" already exists

上的一些答案似乎相当激烈，例如删除所有迁移或使用命令选项，但没有解释导致错误的根本原因

---

你知道如何解决这个错误吗？

试试这个，这样可以：

注意：此字段中的所有数据都将丢失 运行上一次迁移后，您拥有此文件

0009\u auto\u 20180425\u 1129.py

正在等待迁移。。。如果您不再有此文件，请重新运行

makemigrations

，使最后一个迁移文件等待

migrate

在您的情况下，请仔细阅读该文件，并将其放在文件中

0009\u auto\u 20180425\u 1129.py

操作

我想你的数据库里没有任何数据

添加以下行：

migrations.RemoveField(
    model_name='user',
    name='email',
),
migrations.AddField(
    model_name='user',
    name='email',
    field=models.EmailField(blank=True, max_length=254, unique=True, verbose_name='email address'   
),

请随意评论您的评论

---

事实证明，

auth\u user\u email\u 1c89df09\u uniq

关系实际上是一个约束（因此不是数据）。我通过简单地在pgAdmin中删除/删除这个约束来进行迁移，对于类似于

auth\u user\u email\u 1c89df09\u的

索引（之后会弹出一个

ProgrammingError

）

在此之后，我能够迁移：

(venv) Kurts-MacBook-Pro-2:lucy-web kurtpeek$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auditlog, auth, contenttypes, lucy_web, oauth2_provider, otp_static, otp_totp, sessions, two_factor
Running migrations:
  Applying auth.0009_auto_20180425_1129... OK
  Applying lucy_web.0146_auto_20180425_1129... OK

约束和索引已放回

auth_user

表中：

---

makemigrations

不应在

django.contrib.auth

应用程序中生成迁移。您应该尝试找出项目中的哪些代码导致创建此迁移。如果数据库中有任何重要数据，则删除电子邮件字段并重新创建它不是一个好的建议。据我所知，数据库中没有数据。我面临相同的问题，上次迁移成功，但突然出现此错误，此解决方案对数据是否有任何副作用？