Reset database migrations for v3.0 release

[jeremystretch]

Proposed Changes

We should take the upcoming v3.0 release as an opportunity to reset the roughly five years' worth of database migrations we've accumulated since the initial release. I'm not sure yet exactly what the process will entail.

Justification

• Simplifies the deployment process for new users
• Reduces risk of hidden technical debt in older migrations
• Reduces CI testing time

[jeremystretch]

@DanSheps and I have been working on this, and I'm confident in the approach we've arrived at. What we've done is remove and rebuild all database migrations created prior to v2.11.0. Individual migrations from v2.11.0 and later releases have been retained. This means that users will be required to upgrade to a v2.11.x release before upgrading to a v3.0 release.

To test the integrity of the squashed migrations, I compared both the resulting table schemas and the end state of the migrations table. When comparing new installations using the original and squashed migrations, the only differences found in the resulting database schema were the names of some sequences, a cosmetic difference. Further, the only differences found in the resulting migration tables were the addition of the squashed migrations.

I have also tested upgrading a v2.11.0 installation using the squashed migrations with similar results.

As a result of squashing the migrations, we have reduced the time needed to run a complete migration on my local machine from ~84 seconds to ~21 seconds. 🎉 This should help significantly reduce the time needed to run our CI tests.

Testing Methodology

Migration timing:

time ./manage.py migrate

Schema export:

sudo -u postgres psql netbox -c "SELECT table_name, column_name, data_type, column_default, is_nullable, character_maximum_length, numeric_precision FROM information_schema.columns WHERE table_schema = 'public' ORDER BY table_name ASC, column_name ASC"

(Note that we're not using pg_dump for this as manner in which it orders table columns makes the output unsuitable for generating a diff.)

Migrations table export:

sudo -u postgres psql netbox -c "select app, name from django_migrations order by app, name"