#25945: Unabled to refer to partially-run squashed migrations in newer
migrations.
-------------------------+-------------------------------------------------
Reporter: jarekwg | Owner: nobody
Type: Bug | Status: new
Component: | Version: 1.9
Migrations | Keywords: squashmigrations partially run
Severity: Normal | dependencies
Triage Stage: | Has patch: 0
Unreviewed |
Easy pickings: 0 | UI/UX: 0
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From Django docs:
"These files are marked to say they replace the previously-squashed
migrations, so they can coexist with the old migration files, and Django
will intelligently switch between them depending where you are in the
history. If you’re still part-way through the set of migrations that you
squashed, it will keep using them until it hits the end and then switch to
the squashed history, while new installs will just use the new squashed
migration and skip all the old ones."
However there seems to be a caviot in that you can't refer to partially
squashed migrations.
Example:
{{{
my_app/migrations/
0001_initial.py
0002_blah.py -> dep on 0001_initial
0001_initial_squashed_0002_blah.py -> replaces 0001_initial and 0002_blah
0003_ohnoes.py -> dep on ????
}}}
If we try to make 0003 depend on 0001_initial_squashed_0002_blah, then we
get a NodeNotFoundError if the database is only up to 0001_initial: it has
'intelligently switched' to the unsquashed reality in which
0001_initial_squashed_0002_blah does not exist.
Conversely if we try to make 0003 depend on 0002_blah, then we get a
NodeNotFoundError when trying to create a new database: it has
'intelligently switched' to the squashed reality in which 0002_blah does
not exist.
Proposed solution: Use
{{{
dependencies = [('my_app', '0001_initial_squashed_0002_blah'),]
}}}
and for cases where the migration tree does not contain
0001_initial_squashed_0002_blah, have it inspect the 'replaces' list in
0001_initial_squashed_0002_blah.py, pick out the most recent migration (ie
0002_blah.py) and use that instead.
I'm happy to implement this myself if given the thumbs up for the proposed
approach.
--
Ticket URL: <https://code.djangoproject.com/ticket/25945>
Django <https://code.djangoproject.com/>
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