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I'm trying to run a data migration that deletes all rows in a table (say, MyModel). There is another table that points to that table (RelatedModel). The field in the RelatedModel that maps to MyModel has on_delete=models.SET_NULL. When I run the migration, however, I get:
File "/usr/local/lib/python2.7/site-packages/django/db/backends/base/base.py", line 211, in _commit
return self.connection.commit()
IntegrityError: update or delete on table "MyModel" violates foreign key constraint "f2274d6f2be82bbff458f3e5487b1864" on table "RelatedModel"
DETAIL: Key (uuid)=(ywKMUYx7G2RoK9vqqEWZPV) is still referenced from table "RelatedModel".
I added a breakpoint in the migration and checked the SQL DELETE queries. I ran them interactively in the shell and they worked inside the transaction, but the migration still breaks when it tries to commit it. I can't see however which query exactly causes this error, so I don't know how to debug this. Any suggestions? Thanks.
PS: I'm using Django 1.9.13, Python 2.7, PostgreSQL 10.4.
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Documentation and source is available at http://django-debug-toolbar.readthedocs.io/. debug_toolbar is especially useful when you have a query that's failing with a SQL syntax error; it will display the last query that attempted to run (and failed), making it easier to debug.
you can either: temporarily remove your migration, execute python manage.py migrate, add again your migration and re-execute python manage.py migrate. Use this case if the migrations refer to different models and you want different migration files for each one of them.
You can revert by migrating to the previous migration. For example, if your last two migrations are: 0010_previous_migration. 0011_migration_to_revert.
Django keeps track of applied migrations in the Django migrations table. Django migrations consist of plain Python files containing a Migration class. Django knows which changes to perform from the operations list in the Migration classes. Django compares your models to a project state it builds from the migrations.
Use the sqlmigrate command from manage.py . will display the SQL statements for a specific migration of the app.
You can print SQL statements for particular migration by using following management command.
python manage.py sqlmigrate <app label> <migration_name to print sql for>
For an instance if you want to check migration for hello app in your django project and suppose you want to print sql statements for 0001_initial.py. Than you need to execute following line.
python manage.py sqlmigrate hello 0001_initial.py
It would print SQL definations (statements) that will be executed on migration.
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