I have two models: Clause and Template, they have been migrated locally, but I want to delete one of them. The question is: If I just delete it from models.py and admin.py, and run makemigration and migrate, how can I delete and the related DB table as well? Should I delete DB table manualy or the migrations will delete it ?
If you delete one or more from the models.py they will be deleted also in the DB.
The makemigration resets the DB and the migrate command will confirm it.
Related
I have a Django application with a My-SQL database. recently I alter the table_name with the help of MySQL query in the MySQL-shell, after this when I run makemigration and migrate command terminal says "No changes detected". how can i resolve this issue and create again this table with help of Django makemigration and migrate?
can I delete a table from MySQL, any possibility will Django create it again?
If you renamed your table outside Django - you will have to tell Django the new table name like so (using the Meta class):
class Model(models.Model):
name = models.CharField(max_length=255)
class Meta:
db_table = 'new_table_name'
To re-create your table using existing model you need to reset migration for that app to zero and then run migration again
python manage.py migrate APP_NAME zero
python manage.py migrate APP_NAME
It's because the migrations table managed by django doesn't reflect the correct db schema since it was already modified outside of django. If you don't have any important data you can do a migration rollback or recreate the table by hand.
The best way to dela with this is to rename your table back to the original name. Then create a blank migration inside your app and recreate the sql commands you did in the shell inside that migration file. That way django can keep track of the database schema.
You should change the name of the table in models.py not in MySQL shell.
From
class MyModel(models.Model):
...
To
class ThisModel(models.Model):
...
Or Create Proxy Model :
class ThisModel(MyModel):
class Meta:
proxy = True
verbose_name = "ThisModel"
I added a field to one of my models, but in the 'models' folder I have two other python files which have only View models from which I query views in my database. When I run the makemigrations command, the new migrations file that is created includes also adding these view models to my database as tables (which I don't want to). How can I ignore these changes, and only commit the one addition of a field to an actual table on the database.
I think I maybe have to delete the migrations.CreateModel... in the new migrations file and only keep the migrations.addField... , then run the 'migrate' command. I didn't proceed with this because I'm not sure and maybe it will mess up my database in some way.
Thanks in advance to anyone who can help.
when you make a model for database view you must add meta class managed = false and db_table like this:
class MyViewModel(models.Model):
field: models.CharField(max_length=100)
class Meta:
managed = False
db_table = 'database_view_name'
when you write this and run makemigrations a migration generated contains this model but when you run migrate this migration doesnt change anything on database.
you also can create view using migrations in python. see migrations.RunPython for more details
I have one field in my model with like this name = models.CharField(max_length=100, unique=True) but now that table/model have a lot of data and need to change the True to False but without having to drop the table and créate it again, How can I do that?
Generate the new migration using:
python manage.py makemigrations
The above will detect changes to your model and generate a migration class but no execute any sql yet.
To generate/apply the sql to the db:
python manage.py migrate
If you want to see the sql that will be executed before updating the db do this before migrate:
python sqlmigrate {app_label} {migration_module}
EDIT: The above will rename your table with suffix __old, create a new table and insert the data from the old to the new one, and then drop the original table. So not sure if this is what you want..
Another option would be to use plain sql to achieve what you want:
ALTER TABLE table_name DROP CONSTRAINT constraint_name;
But remember, in order keep your migrations updated for new runs, find the migration class that declares your field as unique and change unique=True to unique=False. If any other servers need to be updated you can run the drop constraint command there too so everything is in sync.
Just change the value to False in the model and then makemigrations and migrate. This will update all items in the DB to the new value. This is if you are using the newer version with South and not using syncdb.
The issue is that I create Custom User:
class CustomUser(AbstractUser):
mobile = models.CharField(max_length=16)
address = models.CharField(max_length=100)
And in settings.py write this:AUTH_USER_MODEL = 'login.CustomUser'
And when I run manage.py syncdb for the first time(when db doesn't contains any tables), it throws an error: django.db.utils.ProgrammingError: relation "auth_group" does not exist
But when I run manage.py syncdb when db with tables already exist, then it's okay, just create additional tables. What's wrong to run it when db doesn't contain tables?
Try this
Create a migration directory in the directory of the app containing your custom user model.
Create an empty __init__.py file inside the migration directory.
Execute ./manage.py makemigrations.
Execute ./manage.py migrate.
I think when you use a custom user model, you need to create migrations. Besides, syncdb is already deprecated and will be removed in Django 1.9 so it's better to start using the ./manage.py migrate command.
As the error says, Your CustomUser table has relation with auth_group table, so unless that table is created or exists, you cannot create this new table in db.
When you say 'db with tables already exist, then it's okay', did You create the tables manually or included admin app in your INSTALLED_APPS?
Because if u include admin app, it will automatically create the auth_group table, so you will not see that issue
I have model Foo which resides inside app bar. Now, I wish to move thmodel to app bar2. I am already using db_table when syncdb with bar before
meta:
db_table = 'foo_table'
Now when I do schemamigration with bar, south wants me to delete the table. Is there any ways I can avoid this (table name foo_table is still the same despite changing the app) without manually editing the migration file?
if no changes in database, then you can create empty migrations for both apps in which was this model and which now has this model:
./manage.py schemamigration app1 del_model1 --empty
./manage.py schemamigration app2 add_model1 --empty
south analyze models which described in last migration and on this data he create next migrations