Django遷移：NOT NULL約束失敗

Question

這是我的模型代碼

class student(models.Model):
    name = models.CharField(max_length=100)
    age = models.IntegerField()
    available = models.BooleanField(default=False, blank=True)

在上述模型中，可用的是我的新字段，現在我想遷移數據庫，但是當我按照以下命令運行時，它給我錯誤

python manage.py migrate 

Operations to perform:
  Apply all migrations: student
Running migrations:
  Applying order.0004_auto_20150223_1758...Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
    utility.execute()
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 377, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **options.__dict__)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/base.py", line 338, in execute
    output = self.handle(*args, **options)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 160, in handle
    executor.migrate(targets, plan, fake=options.get("fake", False))
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 63, in migrate
    self.apply_migration(migration, fake=fake)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 97, in apply_migration
    migration.apply(project_state, schema_editor)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/migration.py", line 107, in apply
    operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/migrations/operations/fields.py", line 37, in database_forwards
    field,
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/sqlite3/schema.py", line 167, in add_field
    self._remake_table(model, create_fields=[field])
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/sqlite3/schema.py", line 135, in _remake_table
    self.quote_name(model._meta.db_table),
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/schema.py", line 99, in execute
    cursor.execute(sql, params)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 81, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/home/nikhil/live-devEnv/local/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py", line 485, in execute
    return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: NOT NULL constraint failed: student.available

這里有問題，請給我解決上述問題的方法。

Answer 1

當我想將字段更改為不可為空時，卻遇到了這個問題，但是數據庫中已經有數據，該值為null，這帶來了沖突。 我能夠通過解決

添加可為空的字段。

migrations.AddField(
    model_name='mymodel',
    name='new_field',
    field=models.OneToOneField(to='app.OtherModel', null=True, default=None),
    preserve_default=False,
),

使用RunPython用有意義的東西填充現有數據的字段

migrations.RunPython(fix_null_fields)

最后更改領域是非空

migrations.AlterField(
    model_name='mymodel',
    name='new_field',
    field=models.OneToOneField(to='app.OtherModel'),
    preserve_default=True,
),

這似乎為我工作沒有任何麻煩。 有關更多信息，請查看遷移和遷移操作