#29854: Altering model primary key might cause referred foreign key attribution
inconsistent
-------------------------------------+-------------------------------------
Reporter: Rick Yang | Owner: nobody
Type: | Status: new
Uncategorized |
Component: | Version: 1.11
Migrations | Keywords: MySQL, Migration,
Severity: Normal | Altering primary key,
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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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.
--
Ticket URL: <https://code.djangoproject.com/ticket/29854>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
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