#23577: CREATE INDEX-related OperationalError on migrating renamed models with
colliding field names
----------------------------+--------------------
Reporter: CrimsonZen | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.7
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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This one's a bit of an edge case, but I ran into it trying to refactor
some models on my moderately large work project.
Let's say I have a Django 1.7 app called `sample`:
1. Create a model `Bar`.
2. Create a model `Foo` with `bar = models.ForeignKey(Bar, blank=True,
null=True)`
3. `makemigrations` (migration `0001`)
4. Rename `Foo` to `OldFoo`.
5. `makemigrations`, say yes to the rename prompt (migration `0002`)
6. Create new model `Foo`, which also has `bar = models.ForeignKey(Bar,
blank=True, null=True)`
7. `makemigrations` (migration `0003`)
8. `migrate`
When `migrate` hits `0003`, it throws this error:
{{{django.db.utils.OperationalError: index sample_foo_4350f7d0 already
exists}}}
You may notice that `sqlmigrate sample 0001` and `sqlmigrate sample 0003`
have the same line in both of them:
{{{CREATE INDEX sample_foo_4350f7d0 ON "sample_foo" ("bar_id");}}}
In my production case, I actually had no problems on servers, because
South had created the index with a different name. When I renamed the
models and added a field, the new index did not collide with the old one.
However, our test suite started failing, because it would run the
migrations from the ground up, exposing the above bug.
I haven't decided on a workaround yet, but I thought I'd bring this to
your attention. I might have to inject a migration that renames the index
created in `0001`, or something to that effect.
The attached test case has a project `dj17test` in the state after having
performed all of the above steps.
--
Ticket URL: <https://code.djangoproject.com/ticket/23577>
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