#27092: MIgrations: Creating and then renaming a ForeignKey fails when index and
constraint created
-----------------------------+--------------------------------------
Reporter: alexsdutton | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.10
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
-----------------------------+--------------------------------------
Changes (by alexsdutton):
* needs_better_patch: => 0
* needs_tests: => 0
* needs_docs: => 0
Old description:
> Minimal test case at https://github.com/ox-it/create-rename-foreignkey-
> testcase; example Travis run at https://travis-ci.org/ox-it/create-
> rename-foreignkey-testcase/jobs/153535976.
>
> The following migration fails:
>
> operations = [
> migrations.CreateModel(
> name='Planet',
> fields=[
> ('id', models.AutoField(verbose_name='ID',
> serialize=False, auto_created=True, primary_key=True)),
> ],
> ),
> migrations.CreateModel(
> name='Star',
> fields=[
> ('id', models.AutoField(verbose_name='ID',
> serialize=False, auto_created=True, primary_key=True)),
> ],
> ),
> migrations.AddField(
> model_name='planet',
> name='parent_star',
> field=models.ForeignKey(to='crft.Star'),
> ),
> migrations.RenameField(
> model_name='planet',
> old_name='parent_star',
> new_name='star',
> ),
> ]
>
> as it tries to create the foreign key constraint and index at the end
> against the `parent_star_id` field, which has already been renamed to
> `star_id`.
>
> This arose for as when I wanted to replace a ForeignKey with another to a
> different model, but perform a data migration from the old to the new.
> The idea was: create new foreign key with temporary name, migrate data,
> remove old foreign key, rename the new one to the original name.
>
> I can get round it by first renaming the old field to a temporary name
> and creating the new one with the name we want by the end, but this
> causes the backwards migration to fail for the same reason.
New description:
Minimal test case at https://github.com/ox-it/create-rename-foreignkey-
testcase; example Travis run at https://travis-ci.org/ox-it/create-rename-
foreignkey-testcase/jobs/153535976.
The following migration fails:
{{{#!python
operations = [
migrations.CreateModel(
name='Planet',
fields=[
('id', models.AutoField(verbose_name='ID',
serialize=False, auto_created=True, primary_key=True)),
],
),
migrations.CreateModel(
name='Star',
fields=[
('id', models.AutoField(verbose_name='ID',
serialize=False, auto_created=True, primary_key=True)),
],
),
migrations.AddField(
model_name='planet',
name='parent_star',
field=models.ForeignKey(to='crft.Star'),
),
migrations.RenameField(
model_name='planet',
old_name='parent_star',
new_name='star',
),
]
}}}
as it tries to create the foreign key constraint and index at the end
against the `parent_star_id` field, which has already been renamed to
`star_id`.
This arose for as when I wanted to replace a ForeignKey with another to a
different model, but perform a data migration from the old to the new. The
idea was: create new foreign key with temporary name, migrate data, remove
old foreign key, rename the new one to the original name.
I can get round it by first renaming the old field to a temporary name and
creating the new one with the name we want by the end, but this causes the
backwards migration to fail for the same reason.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/27092#comment:1>
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