django.db.utils.IntegrityError:(1062,键“ slug”的“重复条目””)
我试图遵循tangowithdjango的书,必须添加一个子弹来更新类别表。但是,尝试迁移数据库后出现错误。
http://www.tangowithdjango.com/book17/chapters/models_templates.html#creating-
a-details-
page
我没有提供该Slug的默认值,因此Django要求我提供一个默认值,并按书中的指示输入。
值得注意的是,与其使用原始书籍中的sqlite,不如使用MySQL。
models.py
from django.db import models
from django.template.defaultfilters import slugify
# Create your models here.
class Category(models.Model):
name = models.CharField(max_length=128, unique=True)
views = models.IntegerField(default=0)
likes = models.IntegerField(default=0)
slug = models.SlugField(unique=True)
def save(self, *args, **kwargs):
self.slug = slugify(self.name)
super(Category, self).save(*args, **kwargs)
class Meta:
verbose_name_plural = "Categories"
def __unicode__(self):
return self.name
class Page(models.Model):
category = models.ForeignKey(Category)
title = models.CharField(max_length=128)
url = models.URLField()
views = models.IntegerField(default=0)
def __unicode__(self):
return self.title
命令提示符
sudo python manage.py migrate
Operations to perform:
Apply all migrations: admin, rango, contenttypes, auth, sessions
Running migrations:
Applying rango.0003_category_slug...Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
utility.execute()
File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 338, in execute
output = self.handle(*args, **options)
File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 160, in handle
executor.migrate(targets, plan, fake=options.get("fake", False))
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 63, in migrate
self.apply_migration(migration, fake=fake)
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 97, in apply_migration
migration.apply(project_state, schema_editor)
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 107, in apply
operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 37, in database_forwards
field,
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/schema.py", line 42, in add_field
super(DatabaseSchemaEditor, self).add_field(model, field)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 411, in add_field
self.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/schema.py", line 98, in execute
cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 81, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
File "/usr/local/lib/python2.7/dist-packages/django/db/backends/mysql/base.py", line 128, in execute
return self.cursor.execute(query, args)
File "/usr/local/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 205, in execute
self.errorhandler(self, exc, value)
File "/usr/local/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
raise errorclass, errorvalue
django.db.utils.IntegrityError: (1062, "Duplicate entry '' for key 'slug'")
-
让我们逐步分析它:
- 您要添加
slug
带有的字段unique = True
,这意味着:每个记录必须具有不同的值,而在同一记录中不能有两个记录具有相同的值slug
- 您正在创建迁移:django要求您提供数据库中已经存在的字段的默认值,因此您提供了“(空字符串)作为该值。
- 现在,django正在尝试迁移您的数据库。在数据库中,我们至少有2条记录
- 迁移第一个记录,用空字符串填充子弹列。很好,因为没有其他记录在
slug
字段中有空字符串 - 迁移第二条记录,用空字符串填充子弹列。失败,因为第一个记录在
slug
字段中已经有空字符串。引发异常,迁移中止。
这就是您的迁移失败的原因。您要做的就是编辑迁移,复制
migrations.AlterField
操作两次,在第一个操作中删除unique =
True。在这migrations.RunPython
两次操作之间,您应该放入operation并在其中提供2个参数:generate_slugs
和migrations.RunPython.noop
。现在,您必须在迁移函数内部创建BEFORE迁移类之前,将该函数命名
generate_slugs
。函数应带有2个参数:apps
和schema_editor
。在您的函数中放在第一行:Category = apps.get_model('your_app_name', 'Category')
现在用于
Category.objects.all()
循环所有记录并为每个记录提供唯一的记录。 - 您要添加