Running Migrations in Production

Overview

After deploying to Render, database migrations must be run manually to apply any schema changes.

Running Migrations

Migrations are run locally and pushed to GitHub

1. Make changes to your model.py

2. Generate the migration locally:

flask db migrate -m "describe your change"

3. Commit and push the updated codes to GitHub:

git add .
git commit -m "message"
git push -u origin main

Note

You may have to manually redeploy in Render once the changes are committed to GitHub.

If the Revision ID Changes

If revision ID is out of sync, which can be due to resetting migrations locally, follow these steps:

rm app.db
rm -rf migrations
flask db init
flask db migrate -m "initial migration"
flask db upgrade

Then push to GitHub:

git add .
git commit -m "message"
git push -u origin main

Warning

This will wipe the database clean and you will have to repopulate the database from scratch.

After Every Deploy

If you made any changes to models.py in your deployment:

1. Generate the migration locally

flask db migrate -m "comment"

2. Commit and push the migration files in migration/versions/

3. After Render deploys, run flask db upgrade from the shell tab.

Warning

Never run flask db downgrade or delete files in production as this can cause data loss.

If a Migration Fails

If flask db upgrade fails in production:

1. Check the error message as it usually tells you which column or table caused the issue.

2. Fix migration script locally and push again.