Running migrations with multiple databases

[Shaheed Haque]

Hi,

I'm on Django 4.2 atop Postgres. In my project settings.py, I have a main/default database connection, and a second set up like this:

==============

DATABASES = {
    'default': {
        ...
        'NAME': 'foo',                     # Postgres DATABASE NAME
        ...
    },

    'archive_restore': {
        ...

        'NAME': 'archive_restore',   # Postgres DATABASE NAME

        ...

    },

    # Other entries for specialised purposes such as custom Postgres Foreign Data Wrappers.

===============

As you can see, the Postgres database names are "foo" and "archive_restore" respectively. For all normal Django purposes, we want to use "default", aka "foo". The "archive_restore" connection/database is used in conjunction with a bunch of psql commands to create a subset of the main Django ORM data. Once populated via pg_restore, I need to run the DJango migrations on them for eventual use under Django. I had assumed that a command like this:

./manage.py migrate --database archive_restore

would modify archive_restore/archive_restore. However, what seems to happen is that the migrations are:

• Actually run in default/foo (the migrations include code generated by makemigrations and custom RunPython stuff).
• But recorded in the django_migrations table in archive_restore/archive_restore.

whereas I was expecting that they would be both run and recorded in the latter. Have I overlooked some setting/restriction, or is this a bug?

Thanks, Shaheed

[David Nugent]

Migrations are executed according to how your db routers is setup.

See setting DATABASE_ROUTERS.

Note that normally you would be replicating secondaries, so migrations are normally not applied on all bu the primary, so this is the default.

Regards,

David

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[shahee...@gmail.com]

Thanks: just what I needed to know!