Delete db.sqlite via terminal (Django)-CodePudding

I'm currently deploying a project to Heroku, however it returns me the following error: ValueError: Related model 'store.user' cannot be resolved.

But there is a way to avoid such error locally. You simply do:

py manage.py migrate store

And then

py manage.py migrate

In other words, if I migrate separetely, I won't face such error. However, Heroku migrates all together, then the deploy fails because of this error.

If I proceed locally as Heroku does, i.e. run

py manage.py migrate

I can effortlessly click on and delete the db.sqlite3 file and makemigrations and migrate separetely. Then the issue would be resolved. However, that's not possible when deploying to Heroku. Thus, how can I delete this file only via terminal? I have been searching, but people only say you click on the file and the delete it, which for me it is not possible.

Thanks

CodePudding user response：

However, Heroku migrates all together, then the deploy fails because of this error

Heroku does nothing of the sort.

Migrations only run on Heroku when you tell them to, either by running something like

heroku run python manage.py migrate

or because you have declared a release process that should run when you deploy a new version, e.g.:

web: gunicorn app.wsgi
release: python manage.py migrate

In both cases you are in charge of what that command is. If you don't want to run python manage.py migrate every time you deploy, remove the release process from your Procfile.

if I migrate separately, I won't face such error

This is concerning.

There could be several causes for this. One common issue is missing dependencies in your migration. If you write a migration in app1 that depends on certain models and tables from app2 existing, you need to add a dependency to the relevant migration in app1, e.g. something like this example from the documentation:

class Migration(migrations.Migration):

    dependencies = [
        ('app1', '0001_initial'),
        # added dependency to enable using models from app2 in move_m1
        ('app2', '0004_foobar'),
    ]

    operations = [
        migrations.RunPython(move_m1),
    ]

If migrations are written properly, such that they accurately reflect the code in each commit, build off each other, have dependencies declared, etc. you should always be able to safely apply them to your database.

Finally, you ask about deleting db.sqlite.

Heroku's filesystem is ephemeral. It gets baked into your application slug at build time, and any changes you make to it get reset every time your dyno restarts. This happens frequently (at least once per day).

This means you can't effectively delete your database file. But it also means you can't save data and expect it to be there when you look it up later! SQLite isn't a good fit for Heroku.

A client-server database like PostgreSQL is a much better choice. Heroku offers its own Postgres service with a free tier.

If you switch, I strongly urge you to switch in development as well. Django's ORM makes it relatively easy to change, but database engines aren't drop-in replacements for each other. I've seen real-world examples where developing on SQLite and deploying to Postgres or MySQL causes things to fail in production that worked in development.