Hi, I have recently deleted the directory for an application that I created in Django.

I created the application within an exisitng Django project folder using the following command: python startapp app_name

I then deleted the name of the directory for app_name.

After creating a new application using python runserver startapp new_app, I attempted to make migrations with either python makemigrations or python migrate, I receive the following error message in the terminal:

raise InconsistentMigrationHistory(
django.db.migrations.exceptions.InconsistentMigrationHistory: Migration ExamQuestions.0001_initial is applied before its dependency Exams.0001_initial on database ‘default’.

I am attaching an image of the error message and will appreciate any advice regarding this. Thank you.

If you deleted that directory and everything under it (including the migrations directory), your best bet is to drop the database, delete all migrations from your apps and rebuild the database from scratch.

Suggestion for the future - don’t delete files (or directories) without understanding how that’s going to affect the rest of your project.
Yes, it’s possible to delete Django apps, but it takes more than just deleting a directory to do it cleanly. You should also be aware of how doing something like that might affect an existing installation and your options for upgrading a running system.

You say that I should drop the database.

My question is where is this database located? Within the main directory of the Django project?

It’s located where it is defined in your DATABASES setting. If it’s a sqlite database, then yes, it’s probably easiest just to delete that file. If it’s a PostgreSQL or MySQL/MariaDB database, you would want to drop the database itself.

Thank you Mr. Whitesell! It worked!

Thank you for this help. I have the same problem but the database name in the file is ‘postgres’. How do you delete this database?

You don’t. You shouldn’t be using the default postgres database for your application.

Create a different database for your application, and use it instead.

Thank you. I’ll try that. I am following Will Vincent’s book and wondering if it is OK to stray away from the exact instructions! I thought using the ‘postgres’ database was a bit strange but I was afraid that deployment may not be possible later if I used another db.

Technically it’s fine to use it - it’s just a default database created with PostgreSQL.

It’s ok to delete it too - PostgreSQL will work fine without it. However, many tools and utilities expect it to exist, and it’s usually owned by the postgres system account.

As a learning process, I see nothing wrong with using it. I just wouldn’t do it in a production environment. (That’s a personal perspective.)

Ken - this is so helpful to a newbie like me. I went into postgres via sudo -i -u postgres and created a database called newdb. Then I changed the file to reflect the new database. I’m using docker so I shut that down and did a docker-compose up -d --build and then tried to do makemigrations but the error says “database ‘newdb’ does not exist”.

p.s. I notice that in the file the host is “db” and not “localhost”. Am I trying to create the database in the wrong place and if so how do I find “db”?

The “host” setting is the server hosting the database. It’s not a relevent setting with sqlite because that is a file-based engine that only works locally.

You set the “host” setting to the location of the database. If it’s on the same system, then yes, you can use “localhost”.

(You’re not running Postgres in a container, are you?)

Ken- I’m a bit lost and I don’t want to waste your time.
I’ll hack around a bit more and see if I can fix it. I set the databse to ‘newdb’ and the host to ‘localhost’ but now it’s telling me that the connection to server at ‘localhost’ failed:Connection refused