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Encountering the `relation does not exist` error after updating your Django app on Dokku? Learn how to properly handle migrations and avoid this issue in your PostgreSQL database!
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Solving the relation does not exist Error in Django with PostgreSQL on Dokku

If you're a Django developer, you might encounter the frustrating error message: relation "accounts_articleimageshared" does not exist when updating your application that's deployed on Dokku. This error signals that Django is trying to access a database table that has not been created or recognized. In this post, we will discuss why this happens, how to handle migrations properly, and ensure a smoother update process for your Django application.

Understanding the Problem

When you modify your Django models after an app update, you need to manage your database schema to reflect those changes. This is where migrations come into play. The error you're seeing often arises from not properly applying the migrations that correspond to your model changes.

Common Causes of the Error

Missing Migrations: If you’ve changed your Django models and haven't created the necessary migrations, the database won't have the required tables.

Migration Files Not Applied: Sometimes migrations are created but not applied to your database.

Outdated Codebase: If your code changes (like models) are not yet reflected in the database, this error will manifest.

Step-by-Step Solution

To resolve the relation does not exist error, it's crucial to follow the right sequence of commands and keep track of your migrations. Here’s a structured approach to help you deal with this issue efficiently:

Step 1: Make Changes to Your Code

Modify your Django model as needed. This might involve adding new fields, changing field types, or defining new models.

Step 2: Create Migrations

After making changes, the first command you'll execute is:

[[See Video to Reveal this Text or Code Snippet]]

This step generates migration files based on the changes you made to your models.

Step 3: Apply Migrations to the Database

Next, apply the created migrations using:

[[See Video to Reveal this Text or Code Snippet]]

This step updates your PostgreSQL database with the changes represented in the migration files.

Step 4: Test Your Application

Run tests or check your application to ensure that everything works as expected. It’s always a good idea to verify the functionality before committing changes.

Step 5: Commit Your Changes

After ensuring everything is working fine, don’t forget to commit your migration files along with any other changes:

[[See Video to Reveal this Text or Code Snippet]]

Step 6: Push Changes to Dokku

Finally, push your code and migrations up to Dokku:

[[See Video to Reveal this Text or Code Snippet]]

Avoiding Future Issues

To prevent dealing with the relation does not exist error in the future, consider the following practices:

Maintain Version Control: Always use version control for your migrations. This helps in tracking changes over time.

Regularly Check Migrations: Before deploying updates, ensure that all migrations are up-to-date.

Test Changes Locally: Run your Django application locally and test after every change before deploying to production.

Conclusion

Encountering the error related to relation does not exist can be a daunting experience. However, by following the structured approach outlined in this guide, you can streamline your Django app updates and properly manage migrations in your PostgreSQL database. Implement the steps, and you'll be able to focus more on building rather than troubleshooting!

Remember, proper migration handling is key to maintaining a healthy relationship between your Django application and its database. Happy coding!