#25012: Migration doesn't seem to detect foreignKey type changes
-------------------------------------+------------------------------------
Reporter: Hedde van der Heide | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by Aleksi Häkli):
I was able to neatly fix this with a raw SQL migration that changed the
intermediary table column type.
I had the following schema in an application called `documents`:
{{{
class Tag(models.Model):
# converted this `name` field to primary_key
# previously had the default `id` AutoField as primary_key field
# PrimaryKeyField migration in for ManyToManyField is risky!
name = models.CharField(max_length=32, primary_key=True)
class Document(models.Model):
tags = models.ManyToManyField(Tag, blank=True)
}}}
After changing the schema and running unit tests I discovered that I
indeed to got a DatabaseError:
{{{
django.db.utils.DataError: invalid input syntax for integer: "Miss Amanda
Goodwin"
LINE 1: ..."tag_id") WHERE "documents_document_tags"."tag_id" = 'Miss
Aman...
}}}
Migrating with the following helped:
{{{
ALTER TABLE documents_document_tags ALTER COLUMN tag_id TYPE varchar(32);
}}}
This of course had to be added as a migration file for sane functionality
in tests and migration chain:
{{{
# -*- coding: utf-8 -*-
# Migrations file example for fixing broken ManyToManyField migration from
INTEGER to VARCHAR
# Generated by Django 1.10.3 on 1970-01-01 00:00
from __future__ import unicode_literals
from django.db import migrations
class Migration(migrations.Migration):
dependencies = [
('documents', '0042_auto_19700101-0000'),
]
operations = [
migrations.RunSQL('ALTER TABLE documents_document_tags ALTER
tag_id TYPE varchar(32);'),
]
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/25012#comment:8>
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