Problems adding database columns

Using Django Forms & APIs
1

Hello, everyone,
I have a problem with a model.

The model was initially created:

class Location(models.Model):
    creator = models.CharField(null=False, max_length = 250)
    slug = models.SlugField(null=True)
    checked = models.BooleanField(null=True)
    lat = models.FloatField(null=True)
    lng = models.FloatField(null=True)
    name = models.CharField(null=True, max_length = 250)
    location_name = models.CharField(null=True, blank=False, max_length = 250)

There are various other models that use “ForeignKey” and “OneToOneField” to create a reference to “Location”.

For example, if I now remove “location_name” and run makemigrations:
remove_location_name… OK

It’s all ok.

However, if I now try to add a new database column (makemigrations), e.g.:

class Location(models.Model):
    creator = models.CharField(null=False, max_length = 250)
    slug = models.SlugField(null=True)
    checked = models.BooleanField(null=True)
    lat = models.FloatField(null=True)
    lng = models.FloatField(null=True)
    name = models.CharField(null=True, max_length = 250)
    follower = models.IntegerField(null=True)

I get this error:

django.db.utils.OperationalError: no such column: app_location.follower

Why is that? For all other models - everything works as desired, even in the same app.

2

Search your entire code base to see if you’re referencing that field anywhere in your project. Don’t forget to look for references in things like order_by or in filter functions.

3

Hi Ken,
there are no references to the new field. Even if I:

hsjfwehjbfwe = models.CharField(null=True, max_length = 250)

add to the model and run makemigrationas, this is not accepted, it feels like i can’t add new fields to this model.

4

Ok, maybe I’m a little confused here. Are you getting this message in the makemigrations command or when you try to run your project after you makemigrations?

(Edit: Also, it may be of value if you posted the complete traceback message you’re getting. Sometimes the “real” error is hidden in the full message.)

5

In both situations, as soon as I complete the field in the model.

Therefore:

  1. I complete the model (server is not running)
  2. run makemigrations
  3. error “django.db.utils.OperationalError: no such column: app_location.follower”

or:

  1. I complete the model (server is not running)
  2. run runserver
  3. error “django.db.utils.OperationalError: no such column: app_location.follower”

if I remove it from the code again - everything works, just without the new database field.

6

MacBook-Pro-von-Rene local_fishing % python3 manage.py makemigrations
Traceback (most recent call last):
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/utils.py”, line 84, in _execute
return self.cursor.execute(sql, params)
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/sqlite3/base.py”, line 423, in execute
return Database.Cursor.execute(self, query, params)
sqlite3.OperationalError: no such column: fishing_waters_waters.follower

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File “manage.py”, line 22, in
main()
File “manage.py”, line 18, in main
execute_from_command_line(sys.argv)
File “Library/Python/3.8/lib/python/site-packages/django/core/management/init.py”, line 419, in execute_from_command_line
utility.execute()
File “Library/Python/3.8/lib/python/site-packages/django/core/management/init.py”, line 413, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File “Library/Python/3.8/lib/python/site-packages/django/core/management/base.py”, line 354, in run_from_argv
self.execute(*args, **cmd_options)
File “Library/Python/3.8/lib/python/site-packages/django/core/management/base.py”, line 393, in execute
self.check()
File “Library/Python/3.8/lib/python/site-packages/django/core/management/base.py”, line 419, in check
all_issues = checks.run_checks(
File “Library/Python/3.8/lib/python/site-packages/django/core/checks/registry.py”, line 76, in run_checks
new_errors = check(app_configs=app_configs, databases=databases)
File “Library/Python/3.8/lib/python/site-packages/django/core/checks/urls.py”, line 13, in check_url_config
return check_resolver(resolver)
File “Library/Python/3.8/lib/python/site-packages/django/core/checks/urls.py”, line 23, in check_resolver
return check_method()
File “Library/Python/3.8/lib/python/site-packages/django/urls/resolvers.py”, line 416, in check
for pattern in self.url_patterns:
File “Library/Python/3.8/lib/python/site-packages/django/utils/functional.py”, line 48, in get
res = instance.dict[self.name] = self.func(instance)
File “Library/Python/3.8/lib/python/site-packages/django/urls/resolvers.py”, line 602, in url_patterns
patterns = getattr(self.urlconf_module, “urlpatterns”, self.urlconf_module)
File “Library/Python/3.8/lib/python/site-packages/django/utils/functional.py”, line 48, in get
res = instance.dict[self.name] = self.func(instance)
File “Library/Python/3.8/lib/python/site-packages/django/urls/resolvers.py”, line 595, in urlconf_module
return import_module(self.urlconf_name)
File “/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/importlib/init.py”, line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File “”, line 1014, in _gcd_import
File “”, line 991, in _find_and_load
File “”, line 975, in _find_and_load_unlocked
File “”, line 671, in _load_unlocked
File “”, line 783, in exec_module
File “”, line 219, in _call_with_frames_removed
File “Documents/Projekt Django/local_fishing/local_fishing/urls.py”, line 11, in
path(‘gewaesser/’, include(‘fishing_waters.urls’)),
File “Library/Python/3.8/lib/python/site-packages/django/urls/conf.py”, line 34, in include
urlconf_module = import_module(urlconf_module)
File “/Library/Developer/CommandLineTools/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/importlib/init.py”, line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File “”, line 1014, in _gcd_import
File “”, line 991, in _find_and_load
File “”, line 975, in _find_and_load_unlocked
File “”, line 671, in _load_unlocked
File “”, line 783, in exec_module
File “”, line 219, in _call_with_frames_removed
File “Documents/Projekt Django/local_fishing/fishing_waters/urls.py”, line 2, in
from . import views
File “Documents/Projekt Django/local_fishing/fishing_waters/views.py”, line 148, in
class WaterOverviewView(View):
File “Documents/Projekt Django/local_fishing/fishing_waters/views.py”, line 154, in WaterOverviewView
for entry in Waters.objects.all():
File “Library/Python/3.8/lib/python/site-packages/django/db/models/query.py”, line 280, in iter
self._fetch_all()
File “Library/Python/3.8/lib/python/site-packages/django/db/models/query.py”, line 1324, in _fetch_all
self._result_cache = list(self._iterable_class(self))
File “Library/Python/3.8/lib/python/site-packages/django/db/models/query.py”, line 51, in iter
results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
File “Library/Python/3.8/lib/python/site-packages/django/db/models/sql/compiler.py”, line 1175, in execute_sql
cursor.execute(sql, params)
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/utils.py”, line 98, in execute
return super().execute(sql, params)
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/utils.py”, line 66, in execute
return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/utils.py”, line 75, in _execute_with_wrappers
return executor(sql, params, many, context)
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/utils.py”, line 84, in _execute
return self.cursor.execute(sql, params)
File “Library/Python/3.8/lib/python/site-packages/django/db/utils.py”, line 90, in exit
raise dj_exc_value.with_traceback(traceback) from exc_value
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/utils.py”, line 84, in _execute
return self.cursor.execute(sql, params)
File “Library/Python/3.8/lib/python/site-packages/django/db/backends/sqlite3/base.py”, line 423, in execute
return Database.Cursor.execute(self, query, params)
django.db.utils.OperationalError: no such column: fishing_waters_waters.follower

7

I’d want to take a really good look at your fishing_waters/views.py file. Something is trying to execute model code during initialization.

1 Like
8

Wow - okay, I didn’t expect that at all.

I identified the error, it’s because of this view:

class WaterOverviewView(View):
    template = "fishing_waters/water-overview.html"
    water_name = []
    for entry in Waters.objects.all():
        water_name.append(entry.water_name)
    context = {
        "water_name": water_name,
    }

    def get(self, request):
        return render(request, self.template, self.context )

Thank you Ken!

Addition - this is a view - yes it was stupid to do it like that :smiley:

9

Hello, I know this topic has already been solved. But I have the same problem now and I also did something similar in my views.py file: iterating through my_model.objects.all() with a for loop. My question is: why is it a bad idea? :sweat_smile: I am starting with Django and I thought that practice was okay. Can anybody tell me a better way to do this so that I don’t get this error in the future?

Edit: I say it because I simply commented out the piece of code that was causing the error, and then run again python manage.py makemigrations and everything worked as intended. But what if I had a much bigger project? I don’t think it would be a great idea to be commenting everything out every time I need a new field for a model…

Thanks a lot!

10

This by itself is not a bad idea.

The problem is when you do it in the wrong place (at the module level) instead of in the right place (within a function.)

Solving a specific problem encountered requires seeing the actual error message and the code involved. If you want to get into more specifics, please create a new topic for this conversation.

1 Like
11

Facing a same problem like when i do it on the wrong place at module level instead of right place then specific problem appeared, Looking for a solution

12

As I wrote above, solving a specific problem that you are encountering requires seeing the actual error message and the code involved.
If you are having a problem that you would like assistance with, please create a new topic for this conversation. Include the code causing the error in your post.
When posting code, copy/paste the code into the body of your message, between lines of three backtick - ` characters. This means you’ll have a line of ```, then your code, then another line of ```.

13

heyyy i am getting the same error but dont know how to fixxx . Please Help.
this is my views.py

from django.shortcuts import render,redirect
from .models import Post,BlogComment

Create your views here.

from django.contrib import messages

def blogHome(request):
blogposts = Post.objects.all()
context = {
‘post’: blogposts
}
return render(request, ‘blog/blogHome.html’)
def blogPost(request,slug):
blog = Post.objects.get(slug=slug)
comments = BlogComment.objects.filter(post=blog)
context = {
‘post’: blog, ‘comments’: comments
}
# return HttpResponse(f"This is blogpost where particular blog is rendered {slug} ")
return render(request, ‘blog/blogPost.html’)
def postComment(request):
if request.method ==“POST”:
comment = request.POST.get(‘comment’)
user = request.user
postId = Post.POST.get(‘postId’)
post = Post.objects.get(sno = postId)
comment = BlogComment(comment=comment, user=user,post=post)
comment.save()
messages.warning(request, “your comment has been posted successfully”)
# return HttpResponse(f"This is blogpost where particular blog is rendered {slug} ")
return render(request,‘blog/blogPost.html’)

this is my models.py

from django.db import models
from django.utils.timezone import now
from django.contrib.auth.models import User

class Post(models.Model):
postId = models.AutoField(primary_key=True)

title = models.CharField(max_length=200, unique=True)
slug = models.CharField(max_length=200, unique=True, default="")
category = models.CharField(max_length=200, default="")

author = models.CharField(max_length=10, default="")
updated_on = models.DateTimeField(auto_now= True)
content = models.TextField()
created_on = models.DateTimeField(auto_now_add=True)
thumbnail = models.ImageField(upload_to="images/")


def __str__(self):
    return self.title

class BlogComment(models.Model):
sno = models.AutoField(primary_key=True)
comment = models.TextField()
user = models.ForeignKey(User, on_delete=models.CASCADE)
post = models.ForeignKey(Post, on_delete=models.CASCADE)
parent = models.ForeignKey(‘self’, on_delete=models.CASCADE, null=True)
timestamp = models.DateTimeField(default=now)

this is the error when i added a new field in my model Post (postId)

django.db.utils.OperationalError: no such column: blog_post.postId

Please help me fix it!

14

This topic has been marked as solved. Your post is going to get more attention if you create a new topic for it.
When posting code, copy/paste the code into the body of your message, between lines of three backtick - ` characters. This means you’ll have a line of ```, then your code, then another line of ```.

15

If someone is having a similar issue then they can follow the given steps which worked for me :

  1. Identify the respective views and url file from the terminal error . For example in my case the error was something which included
File "/home/mohit/Desktop/Visual Studio Code/LEARN DJANGO/CE/trydjango/urls.py", line 20, in <module>
    from .views import home_view
  File "/home/mohit/Desktop/Visual Studio Code/LEARN DJANGO/CE/trydjango/views.py", line 10, in <module>
    article_obj = Article.objects.get(id=2)

for me it was views.py in trydjango and urls.py where i was trying to execute model during initialization.

  1. To resolve this issue i simply commented out the all the code that required me to use the model that i have made recent changes to .
# """
# To render HTML Pages    
# """
# from django.http  import HttpResponse
# from articles.models import Article
# from django.template.loader  import render_to_string #,get_template


# # getting data from the  sqlite in this form 
# # article_obj = Article.objects.get(id=2)
# # article_list = Article.objects.all()

# # the context to be passed on to the template has to be a dictionary

# myList = [100,200,300,400,500]
# context ={
#     "article_list":article_list,
#     "title": article_obj.title,
#     "content": article_obj.content,
#     "myList":myList
# }

# # Django Templates

# # using get_template 
# # tmpl = get_template('home-view.html')
# # tmpl_string = tmpl.render(context= context)
# # tmpl_string2 = tmpl.render(context= context)

# # using render_to_string
# HTML_STRING = render_to_string('home-view.html', context=context)

# # this way you can access the arguements , parameters passed in the url
# def home_view(request, id=None,*args,**kwargs):
#     print(args,kwargs)
#     print('id : ', id);  
#     return HttpResponse(HTML_STRING)

also in urls.py

 # path("", home_view),  commented the respective home view.

That worked for me . I was stuck at this issue for more than 2 hrs . I wish you don’t have to spend this long on it.

later i realised that even if we comment only the url path that uses this modified Model it seem to work the same way so you can do that only , no need to comment out the views.py .