Django 模型中没有此类列错误

我正在向 Django 模型添加一个新字段，但无论新字段是什么，当我尝试运行 makemigrations 时都会收到 no such column 错误

File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py", line 318, in execute
  return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: no such column: stats_control.con_LD_file

这是我的模型代码现在的样子。如果注释字段未注释，则“makemigrations”调用将失败，如上面所示。

class Control(models.Model):
    submissions = models.ManyToManyField(Submission, blank=True)
    con_name = models.CharField('name', max_length=200)
    con_bed_file = models.FileField('.bed file', upload_to='controls')
    con_bim_file = models.FileField('.bim file', upload_to='controls')
    con_fam_file = models.FileField('.fam file', upload_to='controls')
    con_SNPs = models.IntegerField('# of SNPs', default = 0, blank=True, null=True)
    #con_LD_file = models.FileField('LD score file', upload_to='LD_scores', blank=True, null=True)
    def __unicode__(self):              # __unicode__ on Python 2
        return self.con_name

编辑：这里还有一些其他的事情

Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/core/management/__init__.py", line 312, in execute
    django.setup()
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/apps/config.py", line 198, in import_models
    self.models_module = import_module(models_module_name)
  File "/Applications/Canopy.app/appdata/canopy-1.5.4.3105.macosx-x86_64/Canopy.app/Contents/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/Users/hugokitano/Documents/Summer_Code/statread/stats/models.py", line 39, in <module>
    class CompareForm(forms.Form):
  File "/Users/hugokitano/Documents/Summer_Code/statread/stats/models.py", line 40, in CompareForm
    select = forms.MultipleChoiceField(widget=forms.CheckboxSelectMultiple,required=False,choices=( (x.id, x.con_name) for x in CONTROL_CHOICES) )          
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/models/query.py", line 162, in __iter__
    self._fetch_all()
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/models/query.py", line 965, in _fetch_all
    self._result_cache = list(self.iterator())
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/models/query.py", line 238, in iterator
    results = compiler.execute_sql()
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/models/sql/compiler.py", line 840, in execute_sql
    cursor.execute(sql, params)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/utils.py", line 97, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/Users/hugokitano/canopy/lib/python2.7/site-packages/django/db/backends/sqlite3/base.py", line 318, in execute
    return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: no such column: stats_control.con_LD_file

设置：

Django settings for statread project.

Generated by 'django-admin startproject' using Django 1.8.3.

For more information on this file, see
https://docs.djangoproject.com/en/1.8/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/1.8/ref/settings/
"""

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
import os

BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/1.8/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = 'igl9^f%j_3&2kk)iuo8lofz%3zzs$v!j+(-#tgl!^==il)k^yo'

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = (
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'stats',
)

MIDDLEWARE_CLASSES = (
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
    'django.middleware.security.SecurityMiddleware',
)

ROOT_URLCONF = 'statread.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'statread.wsgi.application'


# Database
# https://docs.djangoproject.com/en/1.8/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}


# Internationalization
# https://docs.djangoproject.com/en/1.8/topics/i18n/

LANGUAGE_CODE = 'en-us'

TIME_ZONE = 'America/Los_Angeles'

USE_I18N = True

USE_L10N = True

USE_TZ = True


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/1.8/howto/static-files/

STATIC_URL = '/static/'

MEDIA_ROOT = '/Users/hugokitano/Documents/Summer_Code/storage'
MEDIA_URL = 'http://127.0.0.1:8000/stats/media/'

models:

from django.db import models
from django import forms
from django.forms import ModelForm
from django.utils import timezone
from picklefield.fields import PickledObjectField
#from django.contrib.auth.models import User

class Submission(models.Model):
    sub_name = models.CharField(max_length=200)
    sub_file = models.FileField(upload_to='statistics')
    sub_date = models.DateTimeField('date submitted', blank=True, null=True, default=timezone.now)
    def __unicode__(self):              # __unicode__ on Python 2
        return self.sub_name

class Output(models.Model):
    submission = models.OneToOneField(Submission)
    data = PickledObjectField()
    outputFile = models.FileField('Output file', upload_to='outputs', blank = True, null = True)
    numSNPs = models.IntegerField(default=0)

class Control(models.Model):
    submissions = models.ManyToManyField(Submission, blank=True)
    con_name = models.CharField('name', max_length=200)
    con_bed_file = models.FileField('.bed file', upload_to='controls')
    con_bim_file = models.FileField('.bim file', upload_to='controls')
    con_fam_file = models.FileField('.fam file', upload_to='controls')
    con_SNPs = models.IntegerField('# of SNPs', default = 0, blank=True, null=True)
    con_LD_file = models.FileField('LD score file', upload_to='LD_scores', blank=True, null=True)
    def __unicode__(self):              # __unicode__ on Python 2
        return self.con_name

class SubmissionForm(ModelForm):
    class Meta:
        model = Submission
        fields = ['sub_name', 'sub_file'] 

CONTROL_CHOICES = Control.objects.all()

class CompareForm(forms.Form):
    select = forms.MultipleChoiceField(widget=forms.CheckboxSelectMultiple,required=False,choices=( (x.id, x.con_name) for x in CONTROL_CHOICES) )          

class ControlForm(ModelForm):
    class Meta:
        model = Control
        fields = ['con_name', 'con_bed_file', 'con_bim_file', 'con_fam_file'] 

这里的问题是您在模型仍在加载且应用程序未完全初始化时查询数据库：

File "/Users/hugokitano/Documents/Summer_Code/statread/stats/models.py", line 40, in CompareForm
select = forms.MultipleChoiceField(widget=forms.CheckboxSelectMultiple,required=False,choices=( (x.id, x.con_name) for x in CONTROL_CHOICES) )          

CONTROL_CHOICES是文件中先前定义的查询集：

CONTROL_CHOICES = Control.objects.all()

为了简单起见，永远、永远不要这样做。如果您在应用程序未完全加载时查询数据库，一切都会崩溃。

此外，您的代码将不会按预期运行：

class CompareForm(forms.Form):
    select = forms.MultipleChoiceField(widget=forms.CheckboxSelectMultiple,required=False,choices=( (x.id, x.con_name) for x in CONTROL_CHOICES) )          

由于您直接在表单定义中迭代查询集，因此您将获得一个静态元素列表，这些元素在重新启动服务器之前永远不会更改（即使您在数据库中添加新元素）。

这里的解决方案是摆脱forms.MultipleChoiceField and CONTROL_CHOICES并使用ModelMultipleChoiceField https://docs.djangoproject.com/en/1.8/ref/forms/fields/#modelmultiplechoicefield。 它是专门针对这种情况设计的：

class CompareForm(forms.Form):
    select = forms.ModelMultipleChoiceField(queryset=Control.objects.all())

由于查询集是延迟计算的，因此在显示表单时您将直接从数据库中获取最新的对象。 Django 还将为您处理验证和一切。