#29854: Altering model primary key might cause referred foreign key attribution
inconsistent
-------------------------------------+-------------------------------------
Reporter: Rick Yang | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 1.11
Severity: Normal | Resolution:
Keywords: MySQL, Migration, | Triage Stage:
Altering primary key, | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Rick Yang:
Old description:
> Django 1.11.8~16 can reproduce this issue.
> DB is MySQL
>
> Reproduced Steps:
> 1. Create models as following:
>
> {{{
> #!python
>
> class TestModel(models.Model):
> filing_no = models.CharField(max_length=16, primary_key=True)
>
> class OtherModel1(models.Model):
> id = models.AutoField(primary_key=True)
>
> # null=True
> f = models.ForeignKey(TestModel, null=True)
>
> class OtherModel2(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel3(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel4(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel5(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel6(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel7(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel8(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel9(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
>
> class OtherModel10(models.Model):
> id = models.AutoField(primary_key=True)
> f = models.ForeignKey(TestModel)
> }}}
>
> 2. Based on above models, we change max_length of TestModel's filing_no
> and auto-generate migration code as following, and then perform
> migrating.
>
> {{{
> #!python
> migrations.AlterField(
> model_name='testmodel',
> name='filing_no',
> field=models.CharField(max_length=24, primary_key=True,
> serialize=False),
> ),
> }}}
>
> 3. Check DB schema of table OtherModel1, field f's nullable attribution
> becomes False, and field f's nullable attribution in some other
> OtherModel becomes True.
>
> My investigation:
>
> In function BaseDatabaseSchemaEditor._alter_field(), the function call
> _related_non_m2m_objects(old_field, new_field) will return inconsistent
> "old" and "new" related_objects pairs, and generate wrong SQL command to
> alter foreign keys.
New description:
Django 1.11.8~16 can reproduce this issue.
DB is MySQL
Reproduced Steps:
1. Create models as following:
{{{
#!python
class TestModel(models.Model):
filing_no = models.CharField(max_length=16, primary_key=True)
class OtherModel1(models.Model):
id = models.AutoField(primary_key=True)
# null=True
f = models.ForeignKey(TestModel, null=True)
class OtherModel2(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel3(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel4(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel5(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel6(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel7(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel8(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel9(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
class OtherModel10(models.Model):
id = models.AutoField(primary_key=True)
f = models.ForeignKey(TestModel)
}}}
2. Based on above models, we change max_length of TestModel's filing_no
and auto-generate migration code as following, and then perform migrating.
{{{
#!python
migrations.AlterField(
model_name='testmodel',
name='filing_no',
field=models.CharField(max_length=24, primary_key=True,
serialize=False),
),
}}}
3. Check DB schema of table OtherModel1~10, field f's nullable attribution
becomes False, and field f's nullable attribution in some other OtherModel
becomes True.
My investigation:
In function BaseDatabaseSchemaEditor._alter_field(), the function call
_related_non_m2m_objects(old_field, new_field) will return inconsistent
"old" and "new" related_objects pairs, and generate wrong SQL command to
alter foreign keys.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/29854#comment:2>
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