#27860: Changing a CharField to a ForeignKey explodes when migrating in
PostgreSQL
-----------------------------------------+----------------------------
Reporter: Daniel Quinn | Owner: nobody
Type: Uncategorized | Status: new
Component: Migrations | Version: 1.10
Severity: Normal | Keywords: PostgreSQL
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-----------------------------------------+----------------------------
If I have a model that looks like this:
{{{
class MyModel(models.Model):
my_field = models.CharField(max_length=128, db_index=True)
}}}
`makemigrations` will create a migration that looks like this:
{{{
migrations.CreateModel(
name='MyModel',
fields=[
('id', models.AutoField(auto_created=True,
primary_key=True, serialize=False, verbose_name='ID')),
('my_field', models.CharField(db_index=True,
max_length=128)),
],
),
}}}
However, if I later change the field to a `ForeignKey`:
{{{
class MyModel(models.Model):
my_field = models.ForeignKey("alpha.MyOtherModel", blank=True)
}}}
`makemigrations` will create this:
{{{
migrations.AlterField(
model_name='mymodel',
name='my_field',
field=models.ForeignKey(blank=True,
on_delete=django.db.models.deletion.CASCADE, to='alpha.MyOtherModel'),
),
}}}
...which explodes in PostgreSQL (but not SQLite or MySQL) with this:
{{{
psycopg2.ProgrammingError: operator class "varchar_pattern_ops" does not
accept data type integer
}}}
The fix (at least for my case) was to manually break up the `AlterField`
into separate `RemoveField` and `AddField` steps like this:
{{{
migrations.RemoveField(
model_name='mymodel',
name='my_field',
),
migrations.AddField(
model_name='mymodel',
name='my_field',
field=models.ForeignKey(blank=True,
on_delete=django.db.models.deletion.CASCADE, to='alpha.MyOtherModel'),
),
}}}
I ran into this on my own GPL project, and the issue history wherein we
found and fixed the problem is here:
https://github.com/danielquinn/paperless/issues/183
--
Ticket URL: <https://code.djangoproject.com/ticket/27860>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
--
You received this message because you are subscribed to the Google Groups
"Django updates" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/django-updates/054.cb42ab3b2a0562af47bd3c83b0937c84%40djangoproject.com.
For more options, visit https://groups.google.com/d/optout.
