Cast Postgres Boolean type to Small int - demonstration for Django

migration.py

# Generated by Django 3.1 on 2020-08-23 20:44
"""
The SQL statement provided will convert a boolean type in PostgreSQL
to numeric int and then change that to a smallint type. I'm not sure
why I couldn't use small int for blah::smallint::numeric(1,0)...

1 is True and 0 is False
"""

from django.db import migrations, models

SQL = 'ALTER TABLE public_blah ALTER COLUMN "blah" TYPE numeric(1,0) USING blah::int::numeric(1,0);'


class Migration(migrations.Migration):

    dependencies = [
        ('public', '0001_initial'),
    ]

    operations = [
        migrations.RunSQL(SQL),
        migrations.AlterField(
            model_name='blah',
            name='blah',
            field=models.PositiveSmallIntegerField(),
        ),
    ]

models.py

from django.db import models

# Create your models here.
class Blah(models.Model):
    blah = models.PositiveSmallIntegerField()

"""
It used to be 

class Blah(models.Model):
    blah = models.BooleanField()
"""