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:
slug
unique = True
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。
migrations.AlterField
migrations.RunPython
generate_slugs
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:
apps
schema_editor
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。
Category.objects.all()