djangopostgresqldjango-modelsdjango-migrationsdjango-postgresql

Cannot cast type integer to uuid

I tried to run python3 manage.py migrate, but i got this error:

  File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/django /db/backends/utils.py", line 84, in _execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: cannot cast type integer to uuid
LINE 1: ...BLE "core_post" ALTER COLUMN "id" TYPE uuid USING "id"::uuid

I'm using PostgreSQL

My models.py: Link to pastebin

I hope you will help me)

Thank you!

Solution

  • So, basically you started the model without an explicit primary key. So you got a free AutoField and now want them to be UUID's.

    As you can see, Postgres (or any db I know of) doesn't allow changing integers to UUIDs. So you need do a few migrations to get the state you want to:

    First add the uuid field as a normal field with a different name:

    import uuid
from django.db import models

class MyModel(models.Model):
    uuid = models.UUIDField(default=uuid.uuid4, unique=True)

    Run makemigrations and migrate.

    Now make it primary key:

    class MyModel(models.Model):
    uuid = models.UUIDField(default=uuid.uuid4, primary_key=True)

    This should generate a migration that removes the id field and makes uuid primary key (makemigrations and migrate again).

    And finally (if you still want to):

    class MyModel(models.Model):
    id = models.UUIDField(default=uuid.uuid4, primary_key=True)

    Honestly, I don't know if this goes OK, you may have to adjust the generated migration. In either case, you've should now be where you want to be.