#25752: RenameField on m2m causes error when new m2m field is added with old
name
-------------------------------------+-------------------------------------
Reporter: skyjur | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.8
Severity: Normal | Resolution:
Keywords: postgres migrations | Triage Stage:
renamefield | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by skyjur:
Old description:
> When in migrations I do RenameField on ManyToMany field, and then do
> AddField with ManyToMany with same name but different model, I get
> Integrity Error referring to existing index.
>
> It seems the problem is that RenameField does not rename database
> indexes, and then when new m2m field is being added it tries to create
> index with same name and so I get database error:
>
> {{{
> ...
> File "django/db/backends/utils.py", line 64, in execute
> return self.cursor.execute(sql, params)
> File "django/db/utils.py", line 97, in __exit__
> six.reraise(dj_exc_type, dj_exc_value, traceback)
> File "django/db/backends/utils.py", line 64, in execute
> return self.cursor.execute(sql, params)
> django.db.utils.ProgrammingError: relation "cms_test_many_2e06cda4"
> already exists
> }}}
>
> Here is how migration which creates this error looks like:
>
> {{{
> class Migration(migrations.Migration):
>
> dependencies = [
> ]
>
> operations = [
> migrations.RenameField(
> 'test',
> 'many',
> 'many_legacy',
> ),
> migrations.AddField(
> model_name='test',
> name='many',
> field=models.ManyToManyField(to='cms.NewRel2'),
> ),
> ]
>
> }}}
>
> Initially I noticed this error on 1.7, then I also managed to replicate
> it on 1.8
>
> Error happened on postgres database.
New description:
Given I have a field
{{{
many = ManyToManyField()
}}}
I create a migration:
{{{
RenameField: "many" to "many_legacy"
Create Field: "many" as ManyToManyField()
}}}
When I run the migration I get:
{{{
...
File "django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "django/db/utils.py", line 97, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: relation "cms_test_many_2e06cda4"
already exists
}}}
It seems the problem is that RenameField does not rename database indexes,
and then when new m2m field is being added it tries to create index with
same name and so I get database error.
Here is full migration code which throws this error:
{{{
class Migration(migrations.Migration):
dependencies = [
]
operations = [
migrations.RenameField(
'test',
'many',
'many_legacy',
),
migrations.AddField(
model_name='test',
name='many',
field=models.ManyToManyField(to='cms.NewRel2'),
),
]
}}}
Initially I noticed this error on 1.7, then I also managed to replicate it
on 1.8
Error happened on postgres database.
--
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Ticket URL: <https://code.djangoproject.com/ticket/25752#comment:3>
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