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HarmonyOS
我正在使用 Django 1.9 和 MySQL。我想重命名模型中的字段。让我们看看 Django 入门教程 中的模型 Choice 。
class Choice(models.Model):
question = models.ForeignKey(Question)
choice_text = models.CharField(max_length = 200)
votes = models.IntegerField(default=0)
所以，我想将 votes 字段重命名为 votes_count 。我创建了一个空迁移并添加到以下行的操作中：
migrations.RenameField (
model_name='choice',
old_name='votes',
new_name='votes_count',
),
python manage.py migrate 之后，数据库表中的字段被重命名。但是当我尝试使用这个模型时
def vote(request, question_id):
question = get_object_or_404(Question, pk=question_id);
try:
selected = question.choice_set.get(pk=request.POST['choice'])
except (KeyError, Choice.DoesNotExist):
return render(request, 'polls/detail.html', {
'question':question,
'error_message':"You didn't select a choice."
})
else:
selected.votes_count += 1
selected.save()
return HttpResponseRedirect(reverse('polls:results', args=(question_id)))
我有：
“字段列表”中的未知列“polls_choice.votes”
Traceback:
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/mysql/base.py" in execute
112. return self.cursor.execute(query, args)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
226. self.errorhandler(self, exc, value)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in defaulterrorhandler
36. raise errorvalue
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
217. res = self._query(query)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_query
378. rowcount = self._do_query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_do_query
341. db.query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in query
280. _mysql.connection.query(self, query)
The above exception ((1054, "Unknown column 'polls_choice.votes' in 'field list'")) was the direct cause of the following exception:
File "/home/verdigo/venv/lib/python3.4/site-packages/django/core/handlers/base.py" in get_response
149. response = self.process_exception_by_middleware(e, request)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/core/handlers/base.py" in get_response
147. response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "./polls/views.py" in vote
23. selected = question.choice_set.get(pk=request.POST['choice'])
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/manager.py" in manager_method
122. return getattr(self.get_queryset(), name)(*args, **kwargs)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in get
381. num = len(clone)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in __len__
240. self._fetch_all()
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in _fetch_all
1074. self._result_cache = list(self.iterator())
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/query.py" in __iter__
52. results = compiler.execute_sql()
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/models/sql/compiler.py" in execute_sql
848. cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
79. return super(CursorDebugWrapper, self).execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/utils.py" in
__exit__
95. six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/utils/six.py" in reraise
685. raise value.with_traceback(tb)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/utils.py" in execute
64. return self.cursor.execute(sql, params)
File "/home/verdigo/venv/lib/python3.4/site-packages/django/db/backends/mysql/base.py" in execute
112. return self.cursor.execute(query, args)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
226. self.errorhandler(self, exc, value)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in defaulterrorhandler
36. raise errorvalue
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in execute
217. res = self._query(query)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_query
378. rowcount = self._do_query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/cursors.py" in
_do_query
341. db.query(q)
File "/home/verdigo/venv/lib/python3.4/site-packages/MySQLdb/connections.py" in query
280. _mysql.connection.query(self, query)
Exception Type: OperationalError at /polls/1/vote/
Exception Value: (1054, "Unknown column 'polls_choice.votes' in 'field list'")
原文由 verdigo 发布，翻译遵循 CC BY-SA 4.0 许可协议
python
mysql
看起来好像您创建并运行了迁移以将模型字段从
votes重命名为votes_count，但没有同时更新模型。当 Django 尝试从数据库中获取模型时，它会尝试选择
votes列，因为您的模型中仍然有一个 votes 字段，并且出现错误，因为该列不存在于数据库。通常不需要创建手动迁移。通常，您会重命名模型字段，运行
makemigrations，然后运行migrate。让 Django 创建迁移的好处是您可以确信在运行迁移后数据库与您的模型同步。