#27768: makemigrations uses unnecessary AddField for ForeignKey depending on
model
name
----------------------------+--------------------------------------
Reporter: Ed Morley | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
----------------------------+--------------------------------------
Comment (by Ed Morley):
I guess there are two parts to this:
1) When performing a `makemigrations` to generate the initial migrations
file, if the order that the models were declared in models.py was
preserved, then the resultant operations would (a) likely require less
optimization in the first place (since unless people use string references
to other models, they will be declared in the correct order in the file),
and (b) users could at least control the order.
2) Ideally the migrations optimizer would reorder `CreateModel`s (if no
other dependencies between them) rather than refuse to optimize across
them.
ie for (2),
[https://github.com/django/django/blob/e5c2e43cc832028a974399af07a1c3ba6afa2467/tests/migrations/test_optimizer.py#L313-L329
this existing test]:
{{{#!python
def test_create_model_add_field_not_through_fk(self):
"""
AddField should NOT optimize into CreateModel if it's an FK to a
model
that's between them.
"""
self.assertOptimizesTo(
[
migrations.CreateModel("Foo", [("name",
models.CharField(max_length=255))]),
migrations.CreateModel("Link", [("url",
models.TextField())]),
migrations.AddField("Foo", "link",
models.ForeignKey("migrations.Link", models.CASCADE)),
],
[
migrations.CreateModel("Foo", [("name",
models.CharField(max_length=255))]),
migrations.CreateModel("Link", [("url",
models.TextField())]),
migrations.AddField("Foo", "link",
models.ForeignKey("migrations.Link", models.CASCADE)),
],
)
}}}
Should actually be changed to:
{{{#!python
self.assertOptimizesTo(
[
migrations.CreateModel("Foo", [("name",
models.CharField(max_length=255))]),
migrations.CreateModel("Link", [("url",
models.TextField())]),
migrations.AddField("Foo", "link",
models.ForeignKey("migrations.Link", models.CASCADE)),
],
[
migrations.CreateModel("Link", [("url",
models.TextField())]),
migrations.CreateModel("Foo", [("name",
models.CharField(max_length=255)), ("link",
models.ForeignKey("migrations.Link", models.CASCADE)]),
],
)
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/27768#comment:1>
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