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Django migrations on a Lino site¶
Lino applications don’t deliver out-of-the-box Django migrations because the
database schema of a Lino site may also depend on local settings. For
example the languages setting affects your database structure. Or
you may locally disable a plugin. Or some plugin options can cause the
structure to change.
Which just means that you must always run makemigrations before
running migrate.
The migrations directory¶
- migrations¶
Django migrations are automatically enabled on a Lino site when its
site_dir has a subdirectory named
migrations. Lino then automatically sets the migrations_package to the corresponding Python package
name derived from the DJANGO_SETTINGS_MODULE.
Running pm prep without Django migrations¶
Let’s use the lino_book.projects.migs project to play with migrations.
>>> from atelier.sheller import Sheller
>>> shell = Sheller("lino_book/projects/migs")
We begin with Django migrations disabled:
>>> shell("cat clean.sh")
#!/usr/bin/env bash
set -e
rm -rf migrations
rm -f default.db
echo "Removed migrations and database."
>>> shell("./clean.sh")
Removed migrations and database.
The pm prep command works also when Django migrations are disabled. In
this context Django considers all Lino plugins as “unmigrated”. Only some
native Django plugins (contenttypes, sessions, staticfiles) are managed by
Django:
>>> shell("python manage.py prep --noinput")
...
`initdb std minimal_ledger demo demo2 demo_bookings checksummaries checkdata` started on database .../default.db.
...
Operations to perform:
...
Synchronizing apps without migrations:
...
Running migrations:
...
Loading data from ...
...
Update summary data ...
...
27 checks have been run. Found 0 and fixed 15 problems.
Installed 4045 object(s) from 33 fixture(s)
Tidy up:
>>> shell("./clean.sh")
Removed migrations and database.
Running pm prep with Django migrations¶
We enable Django migrations by creating an empty migrations directory
(in the lino.core.site.Site.site_dir).
>>> shell("mkdir migrations") # same as settings.SITE.site_dir.mkdir("migrations")
When Django migrations are enabled, the pm prep command does the same,
but in a different way. Django now considers all Lino plugins as “migrated”:
>>> shell("python manage.py prep --noinput")
...
`initdb std minimal_ledger demo demo2 demo_bookings checksummaries checkdata` started on database .../default.db.
...
Installed 4045 object(s) from 33 fixture(s)
>>> from lino import startup
>>> startup("lino_book.projects.migs.settings")
>>> from lino.api.doctest import *
The application developer can see whether Django migrations are enabled
or not by looking at the
migrations_package site attribute.
>>> print(settings.SITE.migrations_package)
lino_book.projects.migs.migrations
When Django migrations are enabled, Lino automatically fills the
migrations directory with many subdirectories (one for each installed
plugin) and sets the MIGRATION_MODULES setting.
>>> pprint(settings.MIGRATION_MODULES)
...
{'about': 'lino_book.projects.migs.migrations.about',
'accounting': 'lino_book.projects.migs.migrations.accounting',
'appypod': 'lino_book.projects.migs.migrations.appypod',
'bootstrap3': 'lino_book.projects.migs.migrations.bootstrap3',
'cal': 'lino_book.projects.migs.migrations.cal',
'calview': 'lino_book.projects.migs.migrations.calview',
'changes': 'lino_book.projects.migs.migrations.changes',
'channels': 'lino_book.projects.migs.migrations.channels',
'checkdata': 'lino_book.projects.migs.migrations.checkdata',
'comments': 'lino_book.projects.migs.migrations.comments',
'contacts': 'lino_book.projects.migs.migrations.contacts',
'countries': 'lino_book.projects.migs.migrations.countries',
'daphne': 'lino_book.projects.migs.migrations.daphne',
'dashboard': 'lino_book.projects.migs.migrations.dashboard',
'excerpts': 'lino_book.projects.migs.migrations.excerpts',
'export_excel': 'lino_book.projects.migs.migrations.export_excel',
'extjs': 'lino_book.projects.migs.migrations.extjs',
'gfks': 'lino_book.projects.migs.migrations.gfks',
'groups': 'lino_book.projects.migs.migrations.groups',
'help': 'lino_book.projects.migs.migrations.help',
'invoicing': 'lino_book.projects.migs.migrations.invoicing',
'jinja': 'lino_book.projects.migs.migrations.jinja',
'lino': 'lino_book.projects.migs.migrations.lino',
'linod': 'lino_book.projects.migs.migrations.linod',
'lists': 'lino_book.projects.migs.migrations.lists',
'memo': 'lino_book.projects.migs.migrations.memo',
'nicknames': 'lino_book.projects.migs.migrations.nicknames',
'noi': 'lino_book.projects.migs.migrations.noi',
'notify': 'lino_book.projects.migs.migrations.notify',
'office': 'lino_book.projects.migs.migrations.office',
'printing': 'lino_book.projects.migs.migrations.printing',
'products': 'lino_book.projects.migs.migrations.products',
'rest_framework': 'lino_book.projects.migs.migrations.rest_framework',
'restful': 'lino_book.projects.migs.migrations.restful',
'smtpd': 'lino_book.projects.migs.migrations.smtpd',
'storage': 'lino_book.projects.migs.migrations.storage',
'subscriptions': 'lino_book.projects.migs.migrations.subscriptions',
'summaries': 'lino_book.projects.migs.migrations.summaries',
'system': 'lino_book.projects.migs.migrations.system',
'tickets': 'lino_book.projects.migs.migrations.tickets',
'tinymce': 'lino_book.projects.migs.migrations.tinymce',
'topics': 'lino_book.projects.migs.migrations.topics',
'trading': 'lino_book.projects.migs.migrations.trading',
'uploads': 'lino_book.projects.migs.migrations.uploads',
'users': 'lino_book.projects.migs.migrations.users',
'userstats': 'lino_book.projects.migs.migrations.userstats',
'vat': 'lino_book.projects.migs.migrations.vat',
'weasyprint': 'lino_book.projects.migs.migrations.weasyprint',
'working': 'lino_book.projects.migs.migrations.working',
'xl': 'lino_book.projects.migs.migrations.xl'}
TODO: write tests to show a site upgrade using Django migrations.