#24628: Cannot apply migration that depends on squashed migration
----------------------------+--------------------
Reporter: dwt | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------
After some time in the chat with MarkusH, we decided that this should be a
bug report.
Some context: I have quite some migrations (33) of which the first already
was a squash of several migrations. It did get it's 'replaced' field
removed though, as the original migrations it replaced are long gone
already. The goal now was to get that long list of migrations down to one
again, for peace of mind.
This led to the following symptoms: When I created the squashed migration
everything seemed fine. ./manage.py migrate did say that nothing was to be
done (but then again, all the migrations to be squashed where already
applied).
But adding another migration after that ended in tears - ./manage migrate
didn't want to apply it and told me so in no uncertain terms.
{{{
(pycess)dwt@atlan ~/Code/Projekte/pycess/pycess (git)-[master] %
./manage.py migrate
Traceback (most recent call last):
File "./manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File
"/Users/dwt/Code/Projekte/pycess/django/django/core/management/__init__.py",
line 330, in execute_from_command_line
utility.execute()
File
"/Users/dwt/Code/Projekte/pycess/django/django/core/management/__init__.py",
line 322, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File
"/Users/dwt/Code/Projekte/pycess/django/django/core/management/base.py",
line 347, in run_from_argv
self.execute(*args, **cmd_options)
File
"/Users/dwt/Code/Projekte/pycess/django/django/core/management/base.py",
line 398, in execute
output = self.handle(*args, **options)
File
"/Users/dwt/Code/Projekte/pycess/django/django/core/management/commands/migrate.py",
line 86, in handle
executor = MigrationExecutor(connection,
self.migration_progress_callback)
File
"/Users/dwt/Code/Projekte/pycess/django/django/db/migrations/executor.py",
line 19, in __init__
self.loader = MigrationLoader(self.connection)
File
"/Users/dwt/Code/Projekte/pycess/django/django/db/migrations/loader.py",
line 47, in __init__
self.build_graph()
File
"/Users/dwt/Code/Projekte/pycess/django/django/db/migrations/loader.py",
line 281, in build_graph
_reraise_missing_dependency(migration, parent, e)
File
"/Users/dwt/Code/Projekte/pycess/django/django/db/migrations/loader.py",
line 264, in _reraise_missing_dependency
raise exc
File
"/Users/dwt/Code/Projekte/pycess/django/django/db/migrations/loader.py",
line 274, in build_graph
self.graph.add_dependency(migration, key, parent)
File
"/Users/dwt/Code/Projekte/pycess/django/django/db/migrations/graph.py",
line 124, in add_dependency
parent
django.db.migrations.graph.NodeNotFoundError: Migration
process.0002_auto_20150411_1005 dependencies reference nonexistent parent
node ('process', '0001_squashed_initial_2')
}}}
Here we had quite some discussion in #django-dev with MarkusH, of which
the result to me was that a) django doesn't seem to ever record that a
squashed migration is applied, at least as long as it is recognizable by
django as a squashed migration (i.e. it has a .replaced property). b)
there seems to be no way to tell django that the replacing squashed
migration really is already applied for this database.
The last one turned out to be achievable if you remove the old migrations
and the .replaces property from the squashed migration and then apply it
with --fake
MarkusH might want to say more here that he can describe better.
For ease of reproduction I'm attaching the project where this occurred for
me.
--
Ticket URL: <https://code.djangoproject.com/ticket/24628>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
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