Related
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 run python manage.py makemigrations and I get:
No changes detected
Then, python manage.py migrate and I get:
No migrations to apply.
Then, I try to push the changes to production:
git push heroku master
Everything up-to-date
Then, in production, I repeat the command:
heroku run python manage.py migrate
No migrations to apply.
Just in case, I run makemigrations in production:
heroku run python manage.py makemigrations
No changes detected
WHY then I get a
ProgrammingError at ....
column .... does not exist
"No changes detected" means the database is coherent with the code.
How can I debug this?¡?
I got the same problem (column not exist) but when I try to run migrate not with makemigrations (it is the same issue I believe)
Cause: I removed the migration files and replaced them with single pretending intial migration file 0001 before running the migration for the last change
Solution:
Drop tables involved in that migration of that app (consider a backup workaround if any)
Delete the rows responsible of the migration of that app from the table django_migrations in which migrations are recorded, This is how Django knows which migrations have been applied and which still need to be applied.
And here is how solve this problem:
log in as postgres user (my user is called posgres):
sudo -i -u postgres
Open an sql terminal and connect to your database:
psql -d database_name
List your table and spot the tables related to that app:
\dt
Drop them (consider drop order with relations):
DROP TABLE tablename ;
List migration record, you will see migrations applied classified like so:
id | app | name | applied
--+------+--------+---------+
SELECT * FROM django_migrations;
Delete rows of migrations of that app (you can delete by id or by app, with app don't forget 'quotes'):
DELETE FROM django_migrations WHERE app='yourapp';
log out and run your migrations merely (maybe run makemigrations in your case):
python manage.py migrate --settings=your.settings.module_if_any
Note: it is possible that in your case will not have to drop all the tables of that app and not all the migrations, just the ones of the models causing the problem.
I wish this can help.
Django migrations are recorded in your database under the 'django_migrations' table. This is how Django knows which migrations have been applied and which still need to be applied.
Have a look at django_migrations table in your DB. It may be that something went wrong when your migration was applied. So, delete the row in the table which has the migration file name that is related to that column that 'does not exist'. Then, try to re-run a migration.
Here's what i tried and it worked:
Go and add manually the column to your table
run python manage.py makemigrations
go back drop that column you added
run python manage.py migrate
I had a similar issue - the error message appeared when I clicked on the model on the django-admin site. I solved it by commenting out the field in models.py, then running migrations. Following this I uncommented the field and re ran the migrations. After that the error message disappeared.
My case might be a bit obscure, but if it helps someone, it is worth documenting here.
I was calling a function in one of my migrations, which imported a Model of said migration regularly, i.e.
from myApp.models import ModelX
The only way models should be imported in migrations would be using e.g. RunPython:
def myFunc(apps, schema_editor):
MyModel = apps.get_model('myApp 'MyModel')
and then calling that function like so:
class Migration(migrations.Migration):
operations = [
migrations.RunPython(initialize_mhs, reverse_code=migrations.RunPython.noop),
]
Additionally the original import worked until I modified the model in a later migration, making this error harder to locate.
So, I always run into this sort of problem, so today I decided to try and work it out at the database level. Thing is, I changed a model field name which Django didn't bother reflecting in a migration file. I only found out later when I ran into problems. I later looked at the migration files and discovered there was no migration for that change. But I didn't notice because I made other changes as well, so once I saw a migration file I was happy.
My advice. Create migration for each change one at a time. That way you get to see if it happened or not.
So here's my working through it in MySQL.
open mysql console.
show databases; # see all my dbs. I deleted a few
drop database <db-name>; # if needed
use <db-name>; # the database name for your django project
show tables; # see all tables in the database
DESCRIBE <table-name>; # shows columns in the database
SHOW COLUMNS FROM <db-name>; # same thing as above
ALTER TABLE <table-name> CHANGE <old-column-name> <new-column-name> <col-type>; # now I manually updated my column name
If you're using postgresql, just google the corresponding commands.
The issue was in the Models for me, for some reason Django was adding '_id' to the end of my Foreign Key column. I had to explicitly set the related named to the Foreign Key. Here 'Cards' is the parent table and 'Prices' is the child table.
class Cards(models.Model):
unique_id = models.CharField(primary_key=True, max_length=45)
name = models.CharField(max_length=225)
class Prices(models.Model):
unique_id = models.ForeignKey(Cards, models.DO_NOTHING)
Works after changing to:
class Cards(models.Model):
unique_id = models.CharField(primary_key=True, max_length=45)
name = models.CharField(max_length=225)
class Prices(models.Model):
unique_id = models.ForeignKey(Cards, models.DO_NOTHING, db_column='unique_id')
When I get this error, my extreme way to solve it is to reset my database:
Reset your database
For Postgresql on Heroku:
Heroku > your_app > Resources > database > add-ons > click on your database and open it
For postgresql
settings > Reset database
Delete all files in your_app > migrations > __pycache__ except __init.py__
Delete all files in your_app > migrations except __pycache__ folder and __init.py__
Then run:
python manage.py makemigrations
python manage.py migrate
python manage.py createsuperuser
type in to create your superuser, then run:
python manage.py makemigrations
python manage.py migrate
python manage.py
If you are able to inspect your models from your admin section, then it should be all okay now.
Just remove corresponding row migrations for that model in 'django_migrations' model in database.
And re run python manage.py migrate app_name
I tried all these answers with not much luck! What I did to have this problem solved with no harm was to go back through the migration files and find where the actual model was being created for the first time then manually add the field (in the column not being existed error message). Until if you run makemigrations --dry-run you get/see "No changes detected" and that worked. Basically, in my case, I had to carefully take my desired db changes back in time in proper migration file, rather creating a new migration now at the end of migration dependency chain.
Open the latest py file created after running the makemigrations command inside migrations folder of that particular app.
Inside class Migration there is a list attribute called 'operations'.
Remove the particular elements migrations.RemoveField(...).
Save and run python manage.py migrate.
A easier solution to the problem is to make your models exactly like it is in the migration first. and run python manage.py migrate.
Then revert those changes
Run
python manage.py makemigrations
python manage.py migrate
To check for which migrations are applied and which are not, use -:
python manage.py showmigrations
I solved a similar problem by deleting all migrations files (Don't forget to make a backup) and python manage.py makemigrations all of them into one clean file in development and pulling new files on the server. Before then I had dropped existing tables on the PostgreSQL.
I was getting this error for some reason when Django was looking for a column of type ForeignKey named category_id when the actual name in the database was category. I tried every Django solution I could imagine (renaming field, explicitly setting column name, etc.). I didn't want to drop tables or rows as this was a production database. The solution was simply to rename the column manually using SQL. In my case:
ALTER TABLE table_name
RENAME COLUMN category TO category_id;
Make sure you backup your database, ensure this won't break any other applications consuming that particular table, and consider having a fallback column if necessary.
What helped me in the end was simply dropping the database and creating it again as well as deleting all migrations files (including cache). (only removing migrations file didn't work for me at all)
sudo su - postgres
psql
DROP DATABASE 'yourdatabase';
CREATE DATABASE 'yourdatabase';
GRANT ALL PRIVILEGES ON DATABASE 'yourdatabase' to 'yourdjangouser';
then just
python manage.py makemigrations
python manage.py migrate
python manage.py runserver
If you're in development and you make some examples of data that's not important, this step is beneficial for me: just flush your data, make migrations, and migrate:
python manage.py flush
python manage.py makemigrations
python manage.py migrate
After that, you may create a new database from scratch, I hope this information was helpful.
Solved this issue by running
python manage.py migrate
in Heroku Bash shell
I have a django 1.8 app working with a db.
I'm trying to change the schema of a table using the built-in migration.
Here are the steps I did:
In my dev invironment, I grabbed the app source and ran
python manage.py sycdb
then I ran
python manage.py loaddata ~/my_data.json
then I modified modes.py. Added a field and renamed a field...all from the same table 'TABLE1' which had no data.
then
python manage.py makemigrations myapp
python manage.py migrate
Error: django.db.utils.OperationalError: table "myapp_someother_table" already exists
then ran
python manage.py migrate --fake-initial
worked!
but when I browsed to the admin page for TABLE1, I get this error:
OperationalError: no such column: myapp_table1.my_new_field_id
I checked the db and yes, there is no such column.
How can I procceed from here? I prefer to fix this via django.
If I fix it straight in the db, then the migration goes out of sync.
Migrations do not automagically see that you have made changes. Migrations detect changes by comparing the current model with the historical model saved in the migration files.
In this case, you didn't have any historical models, since you didn't have any migrations. Django was not able to detect any changes in your models, even though they were different from your database.
The correct way to make changes to your model is to first run manage.py makemigration <my_app>, and then make the changes to your model, followed by another manage.py makemigrations.
You might not be able to do it via pure django and keep your data. I don't have personal experience with south but there are a lot of mentions if this tool. Just in case if nothing else works for you...
Here is what I did to make things work, but there must be a better way so please add more answers/comments...
I deleted the sqlite db and the migration folder
I made the desired changes to model.py
ran syncdb
ran loaddata to load the json data dump that I had saved previously.
just started the dev server
According to the documentation here:
https://docs.djangoproject.com/en/1.8/topics/migrations/ it says:
migrate, which is responsible for applying migrations, as well as unapplying and listing their status.
and
makemigrations, which is responsible for creating new migrations based on the changes you have made to your models.
From what I understand, I first do
makemigrations
to create the migration file and then do
migrate
to actually apply the migration?
Do note though that I just began my Django project and I added my app to my "installed_apps" list. After that, I did
python manage.py runserver
and it said
You have unapplied migrations; your app may not work properly until they are applied. Run 'python manage.py migrate' to apply them.
It didn't mention anything about running makemigrations.
According the Polls tutorial:
python manage.py makemigrations <app>: Create the migrations (generate the SQL commands).
python manage.py migrate: Run the migrations (execute the SQL commands).
As Django's documentation says Migrations are Django’s way of propagating changes you make to your models (adding a field, deleting a model, etc.) into your database schema.
makemigrations basically generates the SQL commands for preinstalled apps (which can be viewed in installed apps in settings.py) and your newly created apps' model which you add in installed apps.It does not execute those commands in your database file. So tables doesn't created after makemigrations.
After applying makemigrations you can see those SQL commands with sqlmigrate which shows all the SQL commands which has been generated by makemigrations.
migrate executes those SQL commands in database file.So after executing migrate all the tables of your installed apps are created in your database file.
You can conform this by installing sqlite browser and opening db.sqlite3 you can see all the tables appears in the database file after executing migrate command.
As we know Django is an ORM (Object Relational Mapping). When we use the command:
python manage.py makemigrations [app_name]
It will generate the sql command to create the table corresponding to each class you made in models.py file.
then the command:
python manage.py migrate [app_name]
will create the table in database using the commands which have been generated by makemigrations.
For example, if we make a model class-
from django.db import models
class Person(models.Model):
first_name = models.CharField(max_length=30)
last_name = models.CharField(max_length=30)
The corresponding sql command after using makemigrations will be
CREATE TABLE myapp_person (
"id" serial NOT NULL PRIMARY KEY,
"first_name" varchar(30) NOT NULL,
"last_name" varchar(30) NOT NULL
);
and using above command, table will be created in the database when we use migrate.
You should run the command -migrate- after adding a new app under the INSTALLED APPS section in the settings.py file in order to synchronize the database state with your current set of models. Assuming you've already modified the models.py file.
When you run -makemigrations- it packages up changes to your model into individual migration files.
Normally you would first run makemigrations and then migrate.
See documentation on Django Models
It is necessary to run both the commands to complete the migration of the database tables to be in sync with your models.
makemigrations simply analyzes your current models for any changes that would be out of sync with your database and creates a migrations file that can be used to bring the in sync. If left at this point, your models would still be out of sync with your database possibly breaking your code that queries the database.
migrate is the command to "Make It So!" and apply the changes noted during the makemigrations phase.
Source
This is django's replacement for the old manual south way of making migrations, they can be used to catalog changes in your models and write out changes that will take place in the db.
Migrate is basically the old syncdb but it takes into account all the migrations made by makemigrations.
makemigrations: creates the migrations (generating SQL Command- not yet executed)
migrate: run the migrations (executes the SQL command)
But in your case, Django is asking you to migrate the DEFAULT migrations which should run before first running of server. This would have been the same warning without even creating the first app.
Make migrations : Basically it generate SQL Commands for preinstalled apps and newly created app model which you added in installed app. It dose not executed SQL commands in your database. So actual tables are not created in DB.
Migrate : Migrate execute those SQL commands which are generated by make-migration in Database file . So after migrate all the tables of installed app are created in DB.
According to the second tutorial of the django tutorial series. Migrations are:
The migrate command takes all the migrations that haven’t been applied (Django tracks which ones are applied using a special table in your database called django_migrations) and runs them against your database - essentially, synchronizing the changes you made to your models with the schema in the database.
So pretty much all it does is:
When you execute the make migrations command you're saving the 'instructions' to mysql
When you execute the migrate command, you're executing those same instructions
I'm using sqlite3 and pycharm to learn more about django, and googled to find that south is recommended to make it easier to modify models after they have been created.
I'm trying to follow the advice on http://south.aeracode.org/docs/tutorial/part1.html#starting-off.
The most success I've had so far is to create a simple model and run syncdb before adding south to installed_apps. That way the intial tables are created and I get a chance to create a super user. (Django admin seems to fret if there are no users).
Then I add south to installed_apps, and run django_manage.py schemamigration bookmarks --initial
It seems to work fine. A new directory is created called migrations with a couple of files in it in my app folder and an encouraging message.
"Created 0001_initial.py. You can now apply this migration with: ./manage.py migrate bookmarks"
The next step - django_manage.py" migrate bookmarks generates the following error message
django.db.utils.DatabaseError: no such table: south_migrationhistory.
I thought that table would be created in the first schememigration step. What am I missing? Can anyone help?
Marg
South uses a table if its own to keep track of which migrations have been applied. Before you can apply any migrations, this must have been created, using python ./manage.py syncdb.
As well as for setting up south, you will find syncdb sometimes necessary for non-south apps in your project, such as the very common django.contrib.auth.
Note that as a convenience, you can run both in one go like this
python ./manage.py syncdb --migrate
My latest (unsuccessful) effort was the following
Create application – synch db – superuser created
Test run –admin screen shows basic tables
Add south, and syncdb from command line with manage.py syncdb – south_migrationhistory table created. Add basic vanilla model
Tried various combinations of manage.py syncdb –manage, and
schemamigration from Pycharm (if run from within pycharm a
migrations directory is created within the app
– if run from the command line the directory does not seem to be
created.)
Django admin screen shows table – but if I try to edit
the table it says that it doesn’t exist
Check database structure
using SQLite browser - table for newly created model doesn’t exist
I’m starting to think that the whole thing is not worth the time wasting hassle – maybe I’m better off just modifying the tables in SQLite browser
Answer in the similar question:
Run syncdb to add the Django and South tables to the database.