Opened 10 years ago

Closed 10 years ago

Last modified 10 years ago

#24447 closed Bug (fixed)

Migrations do not add a FK constraint for an existing column

Reported by: Jean-Louis Fuchs Owned by: nobody
Component: Migrations Version: 1.7
Severity: Normal Keywords:
Cc: Markus Holtermann Triage Stage: Ready for checkin
Has patch: yes Needs documentation: yes
Needs tests: no Patch needs improvement: yes
Easy pickings: no UI/UX: no

Description (last modified by Jean-Louis Fuchs)

Pull request: ​https://github.com/django/django/pull/4235

Consider following model:

class ForeignKeyTest(models.Model):
    id = models.AutoField(primary_key=True)
    customer = models.IntegerField()

class Customer(models.Model):
    id = models.AutoField(primary_key=True)

Then it gets migrated to this:

class ForeignKeyTest(models.Model):
    id = models.AutoField(primary_key=True)
    customer = models.ForeignKey('Customer')

class Customer(models.Model):
    id = models.AutoField(primary_key=True)

The second migration won't create the foreign key. This does not fail with sqlite! Because these migrations are handled differently. It will fail with MySQL and probably Postgres too.

The code didn't detect this case: if old_field.rel doesn't exist alter_field() must always create the foreign key and ONLY if .rel exists it must check .db_constraint, too. Since no .rel also means there was no foreign key before.

Change History (8)

comment:1 by Tim Graham, 10 years ago

Patch needs improvement: set
Triage Stage: Unreviewed → Accepted

comment:2 by Markus Holtermann, 10 years ago

Version: master → 1.7

comment:3 by Markus Holtermann, 10 years ago

Cc: Markus Holtermann added
Needs documentation: set

comment:4 by Jean-Louis Fuchs, 10 years ago

Description: modified (diff)
Summary: Migrations do not execute create_fk_sql() when adding a foreign key to a field → Migrations do not add a FK constraint for an existing column

Removed redundant information and chose clearer title.

comment:5 by Markus Holtermann, 10 years ago

Triage Stage: Accepted → Ready for checkin

RFC when remaining style update is done

comment:6 by Markus Holtermann <info@…>, 10 years ago

Resolution: → fixed
Status: new → closed

In f4f0060feaee6bbd76a0d575487682bc541111e4:

Fixed #24447 -- Made migrations add FK constraints for existing columns

When altering from e.g. an IntegerField to a ForeignKey, Django didn't
add a constraint.

comment:7 by Markus Holtermann <info@…>, 10 years ago

In 1ae2df6bfc3afadd7edb29a5887711f70cdb52c6:

[1.8.x] Fixed #24447 -- Made migrations add FK constraints for existing columns

When altering from e.g. an IntegerField to a ForeignKey, Django didn't
add a constraint.

Backport of f4f0060feaee6bbd76a0d575487682bc541111e4 from master

comment:8 by Markus Holtermann <info@…>, 10 years ago

In 283b630d6324c936cbe42d8f0169f056b3ba59c6:

Fixed #24447 -- Made migrations add FK constraints for existing columns

When altering from e.g. an IntegerField to a ForeignKey, Django didn't
add a constraint.

Backport of f4f0060feaee6bbd76a0d575487682bc541111e4 from master

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