I made two changes to different models in my database.
The first
operations = [
migrations.DeleteModel(
name='Settlement',
),
]
And the second:
operations = [
migrations.RemoveField(
model_name='invoice',
name='settlement_deducted',
),
migrations.RemoveField(
model_name='invoice',
name='settlement_supporting',
),
]
The issue is that they ran in this order, and the second one failed. The field being removed in the second migration uses the "Settlement" model, but since that model was deleted in the first migration it throws this error:
ValueError: The field invoices.Invoice.settlement_deducted was declared with a lazy reference to 'accounting.settlement', but app 'accounting' doesn't provide model 'settlement'.
The field invoices.Invoice.settlement_supporting was declared with a lazy reference to 'accounting.settlement', but app 'accounting' doesn't provide model 'settlement'
Now when I try to do anything to fix it, it seems to just be stuck in that error state and continuously throws that same error.
I have tried reverting the first migration to the previous migration on that model, adding that model back in and running makemigrations and then migrate so that the Settlement model exists again, and deleting the second migration (though it was never run anyway). All of these options are still throwing the same error.
I am surprised that Django didn't catch this dependency issue for me, but it is unfortunately too late for that now. I also tried adding it as a dependency, but then it just threw the error saying that a migration has been migrated before one of its dependencies.
I was successfully able to solve the issue! These are the steps I took:
add the second migration as a dependency to the first one
go to the django_migrations table in the db and delete the first migration (which ran already)
run ONLY the second migration
fake the first migration (since it already ran)
(unnecessary step but necessary in my case) run migrate normally to finish migrating uninvolved migrations from other apps
insite try this
py manage.py migrate <yourappname> zero
then go in the same app folder and in that migration folder delete all the file except pycache and init.py and then again try to run
py manage.py makemigrations
py manage.py migrate
and please do replace py with python if you are using any other Os then windows what the migrate zero do is it delete all the migration of your app and after again doing the migration it will get everything back for you
and tell me if you still got any other error
Related
So I had to reorganize my models ( had to do manual migrations) and in the end I had to rename some models and then I got an error, when I was running `manage.py migration:
The field Collect_data.Players.Team was declared with a lazy reference to 'xx.old_name', but app 'xxx' doesn't provide model 'old_name'.
the migration file:
migrations.RenameModel(
old_name='Old_name',
new_name='new_name',
),
Now if look to the db, everything seems to be ok(renaming has been done) and all the connections are ok. If I open django shell, I can get the models with new names. Only problem is that I get this warning when I run server: "You have 1 unapplied migration(s)." and if I try to migrate, then I get a error that table already exists. If I run makemigartion I get same error as the first one said ( lazy reference... ). In migrations list I can see that the last migration doesn't have "X" on it's box. So how can I tell Django that everything is fine?
python manage.py migrate --fake ####
This tells django to do a fake migration, basically check the migration checkbox without doing anything.
'####' is the migration file number you want to fake it
I have a Postgres database full of data. And I made several changes to my Django app models.
mange.py makemigrations worked fine and created the migration files. But manage.py migrate execute only one file. And when I launch it again it doesn’t execute the rest as if they are already applied.
I deleted the migration files that were not applied and did another makemigration but it says no changes detected.
Any ideas how to reflect the models changes on the database without losing the data ?
Thanks
Django keeps track of which migrations it has applied already, so when you run the migrate command it will execute only the migrations that Django thinks that are missing.
I deleted the migration files that were not applied and did another makemigration but it says no changes detected.
This was a bad idea, it will make your migrations inconsistent.
If you want to go back in time, instead of deleting migrations, the proper way to do this is by reverting migrations. You can use the same migrate command and specify to which migration point you want your database model to be.
Check this answer for further information about reverting migrations; django revert last migration
As I was changing my models.py and migrating, I got an error message saying:
python manage.py makemigrations project_profile
CommandError: Conflicting migrations detected; multiple leaf nodes in the migration graph: (0033_auto_20180217_0912, 0036_auto_20180217_0927 in project_profile).
To fix them run 'python manage.py makemigrations --merge'
So, when I tried to follow the instructions, I got another error that one of my tables that the merged migration is now depending on do not exist anymore (I renamed it). Interestingly enough, this renaming took place during the merge operation. So, really Django should have known about it in the first place.
To resolve the situation, I deleted prior migrations up to and including the migrations that was not applied, the one that caused all the headache. I tried to makemigrations and migrate again. But, Django now throws another error saying some of the models it wants to create in the database already exist. Obviously, I do not want to delete those tables and loose all that information to appease Django. So, I had to resort to some hacking solutions and actually change those tables manually and do a fake migration in order to stop Django from complaining.
Having said all of that, I feel like there should be a more logical way about this. How do I resolve migrations during the merging?
I had the same issue, Then I was able to solve this by deleting the migrations file that django pointed out and starts with name auto. It occurred 2-3 times before it finally gave up and finally worked.
Alternatively you can django-dbbackup or django-import-export packages to backup the tables then clean your database and migrations. Then you can restore them back to the same state once migrations are stable.
Sources
dbbackup : https://django-dbbackup.readthedocs.io/en/stable/
import-export : https://django-import-export.readthedocs.io/en/latest/index.html
I have trouble with django model migrations.
I have some models in my app, and I already have some data inside.
When I added some models in my application, and I run makemigrations, the app report that there is no change.
I know that sometimes some errors came when migrate, so I delete django_migrations table in my database and run makemigrations again, and now program found my new fields.
The problem now is that if I run migrate system tell me that some tables already exist. (Which is ok and correct, because they do). I don't want to delete those tables, because I have data already inside.
I can't run migrate --fake, because program will think that I already have all the tables, which is not true.
So, I am looking for a way to tell the program : run migration, if table exist skip it. (--fake it)
Another question is why is this happening to me, that makemigrations don't recognise my changes (some cache problems,...)?
How about doing this way ?
python manage.py makemigrations
(Skip this step if you have already have migration file ready)
It will create migrations for that package lets say with a name like 0001_initial.py
Edit the file manually so that you delete all models there except that was already created in database.
Now you do a fake migration. This will sync your database with models.
python manage.py migrate --fake
Then run makemigrations again to have rest of the tables created along with a new migration file.
python manage.py makemigrations
Regarding your other question, Why makemigrations didn't recogonize your models can be because of reasons like:
Migrations for those changes are already there in some migration file.
You missed it to mention package_name in INSTALLED_APPS but i believe you did it here.
every time you make changes to your models, try these steps :
python manage.py makemigrations [your app name]
then:
python manage.py migrate
it should work fine. but remember if you have already data(rows) in your tables you should specify the default value for each one the queries.
if not, Django prompt you to specify the default value for them
or you can just try to use blank=True or null=True in your fields like below :
website = models.URLField(blank=True)
the possible cause or this is that you have another migration in the same folder starts with the same prefix... maybe you make another migration on the same table on another branch or commit so it's saved to the db with the same prefix ie: 00010_migration_from_commit_#10, 00010_migration_from_commit_#11
the solution for this is to rename the migration file like this 00011_migration_from_commit_#11
I tried to edit the related migration file and commented the part where it creates that specific column, then ran python manage.py migrate
The main problem is the existing tables that are disabling the migration of the new tables, so the solution is straight-forward:
** Try to add managed = False to the existing dB so it won't be detected by migrate
** Redo it for all existing old tables :
class Meta:
managed=False
It sometimes gets boring when we have a lot of tables in the same application but it works perfectly!
I have created a model and executed syncdb which had created the tables as my model was designed.
Afterwards I modified the model and executed makemigrations which created the migrations ignoring the tables that syncdb had already created.
So I ended up with an error "relation already exists".
Why did makemigrations created everything from scratch?
How do I fix this situation ?
makemigrations creates new migrations based on the changes detected to your models.
Also, one thing to note is syncdb command is deprecated since Django 1.7 and will be removed in Django 1.9. So, you should use the migrate command.
From syncdb docs:
Deprecated since version 1.7:
This command has been deprecated in
favor of the migrate command, which performs both the old behavior as
well as executing migrations.
makemigration always creates one migration file having all the changes. So, when you run makemigration for first time it tries to find the previous migration file. if not found it creates one initial migration file. And when it tries to apply it to the db it finds the relation already exists. And thus throws error.
Best practice is, before updating model, create one migration then modify the model.