Django-migration-dbindex-check

Automatically check your Django migrations for a new db_index=True

This package checks your Django project for any migrations that have new database indices and lets you know where they are. It's designed to be implemented ad a CI check to warn you before deployment.

Why do I need this?

The default behaviour of most SQL databases when creating a new index is to lock the specified table and scan each row sequentially. On existing projects with large databases this can take some time and will cause downtime on your production application. This check will warn you, allowing you to migrate out of hours, use Postgres' CONCURRENTLY feature or schedule downtime.

Installation

Install from pypi - pip install django-migration-dbindex-check

Install from git repo - pip install -e git+https://github.com/PrimarySite/django-migration-dbindex-check.git#egg=django-migration-dbindex-check

Usage

The package is designed to be used from the command line:

1. Activate your virtualenv if required.
2. Navigate to your projects root folder.
3. python -m django-migration-db-index-check

or

1. Activate your virtualenv if required.
2. python -m django-migration-db-index-check <your_root_path>

The script will then output a list of offending migrations or stderr as per this example:

A new db_index was added to field:<field> in model:<model> in app:<app>. This was added in migration <migration>.

The script will exit with a non-zero status code if a new db_index has been found.

Ignoring Migrations

Once you've been warned about the issue, you won't want your CI checks to fail forever. There are two ways to ignore migrations.

In your project root, create a file called migrations_check.cfg following the example below.

[DJANGO_MIGRATION_DBINDEX_CHECK]
important_functionality = 4
other_service = 4
the_app = 4

exclude_paths=
    venv,
    some/other/path

In the top section, each row follows the format <app_name> = <ignore_upto_migration>. So in this example, all migrations for the app important_functionality will be ignored up to (but not including) 0004_my_migration.py.

It's also common to want to ignore entire directories (for example your venv folder), to do this add your directory path to the exclude_paths variable. Note that this will check for each string anywhere in the filepath so be specific.