relation "app_table" does not exist LINE 1: SELECT COUNT(*)

Heya,

The error relation "app_table" does not exist indicates that the PostgreSQL database doesn’t recognize the table associated with your Django model. There could be various reasons for this:

1. Incomplete Migrations: Even if makemigrations and migrate appeared to work, there might have been a hiccup.
2. Database Settings: There might be a mismatch between the database your Django app is connected to and the one you ran migrations against.
3. Database Router: If you’re using database routers in Django to route certain apps to specific databases, there might be a misconfiguration.

Let’s go through potential solutions step by step:

1. Check Migration Files:

Ensure that the migration file created for the new model is correct. Look inside the migrations folder of your app and find the specific migration related to the creation of the new model.

2. Ensure You’re Using the Right Database:

Check your settings.py to see if you’re connecting to the expected database. This is a common issue, especially if you have multiple databases or environments.

3. Re-apply Migrations:

Sometimes, re-applying migrations can help:

python manage.py migrate app_name zero
python manage.py migrate app_name

This rolls back the migrations for the app (without deleting data for unrelated tables) and then re-applies them.

4. Database Router:

If you’re using multiple databases, ensure that you’ve set up the database routers correctly. The issue might be that your model is routed to a different database than you expect.

5. Manual SQL Check:

Connect to your PostgreSQL database directly:

psql -U your_username -d your_database_name

Then, check if the table exists:

\dt

This command lists all tables. Ensure your table is in the list.

6. Check PostgreSQL Logs:

You can check the PostgreSQL logs for any errors or issues. The logs might provide more detailed information about any issues related to table creation.

7. Backup First:

Before making any significant changes, especially if you’re considering rolling back migrations or altering the database schema, always back up your database. You can do this using the pg_dump command:

pg_dump your_database_name > backup.sql

This will create a backup file named backup.sql.

Conclusion:

The issue you’re facing is a common one with various potential causes. By carefully diagnosing the problem and checking each possibility step-by-step, you can typically resolve it without resorting to drastic measures like removing the entire database.

Hi there,

If you were to run python manage.py showmigrations are your migrations listed as 'applied`?

What I could suggest is connecting to your Postgres database using psql or any other SQL client, and verifying that the database and the database tables actually exist. If you do that with psql you can follow the steps here:

How to show all tables in PostgreSQL?

If everything looks good, I could suggest trying to reset the migrations and running them again from scratch.

Let me know how it goes!