Django 1.8 migration unable to cast column id to integer

Question

I\'m migrating my site from an SQLite backend to a Postgres backend. We\'ve been running native-Django style migrations (i.e., not South) from the beginning of the project. Most

Answer 1

Postgres doesn't know how to convert a boolean field into an integer, even if the table is empty. You need to tell it with a using clause. You can use an SQL migration for the integer conversion before you convert to a foreign key. I don't think there's a way to do this without any SQL, django doesn't know how to do that.

ALTER_SQL = '''
    ALTER TABLE processes_process ALTER COLUMN milestone TYPE integer USING (
        CASE milestone
            when TRUE then ...
            when FALSE then ...
        END
        );
    '''

class Migration(migrations.Migration):

    dependencies = [
        ('processes', '0002_auto_20150508_2149'),
    ]

    operations = [
        migrations.AlterModelOptions(
            name='process',
            options={'ordering': ['milestone', 'sequence'], 'verbose_name_plural': 'processes'},
        ),
        migrations.RunSQL(ALTER_SQL, None, [
            migrations.AlterField(
                model_name='process',
                name='milestone',
                field=models.IntegerField(),
                preserve_default=True,
            ),
        ]),
        migrations.AlterField(
            model_name='process',
            name='milestone',
            field=models.ForeignKey(to='processes.Milestone'),
        ),
    ]

If the table is empty, you might be able to get away with an empty using clause or an empty case.