Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (pypi.python.org).
Help us improve Python packaging - Donate today!

Add database table-level constraints to your Django model's Meta

Project Description
# django-db-constraints

## What is this?

Add database table-level constraints to your Django model's Meta class and have `makemigrations` add the appropriate migration.

```python
class Foo(models.Model):
bar = models.IntegerField()
baz = models.IntegerField()

class Meta:
db_constraints = {
'bar_equal_baz': 'check (bar = baz)',
}
```

This should generate a migration like so:

```python
class Migration(migrations.Migration):

initial = True

dependencies = [
]

operations = [
migrations.CreateModel(
name='Foo',
fields=[
('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
('bar', models.IntegerField()),
('baz', models.IntegerField()),
],
),
django_db_constraints.operations.AlterConstraints(
name='Foo',
db_constraints={'bar_equal_baz': 'check (bar = baz)'},
),
]
```

The resulting SQL applied:

```sql
CREATE TABLE "sample_foo" ("id" serial NOT NULL PRIMARY KEY, "bar" integer NOT NULL, "baz" integer NOT NULL)
ALTER TABLE "sample_foo" ADD CONSTRAINT "bar_equal_baz" check (bar = baz)
```

## Composite foreign keys

It's possible to support composite foreign keys if you have a unique key on your reference model:

([Why are composite foreign keys useful?](https://github.com/rapilabs/blog/blob/master/articles/same-parent-db-pattern.md))

```python
class Bar(models.Model):
baz = models.IntegerField()

class Meta:
unique_together = ('id', 'baz')


class Foo(models.Model):
bar = models.ForeignKey(Bar)
baz = models.IntegerField()

class Meta:
db_constraints = {
'composite_fk': 'foreign key (bar_id, baz) references sample_bar (id, baz)',
}
```

Results in:

```sql
ALTER TABLE "sample_foo" ADD CONSTRAINT "composite_fk" foreign key (bar_id, baz) references sample_bar (id, baz)
```

## Migration operation ordering

Given that nothing will depend on a constraint operation, they're simply added to the end of the list of operations
for a migration. This includes operations that drop fields used in a constraint as the database drop will any related
constraints as well (at least with PostgreSQL).

## Caveats

It's possible to end up in a situation where the constraints are declared on the Meta class but do not exist in the database
due to a database dropping a constraint implicitly when a field in the constraint is dropped.

## Installation

```
pip install django-db-constraints
```

in your settings.py:

```python
INSTALLED_APPS = [
'django_db_constraints',

]
```


Release History

Release History

This version
History Node

0.3.0

History Node

0.2.0

Download Files

Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

File Name & Checksum SHA256 Checksum Help Version File Type Upload Date
django_db_constraints-0.3.0-py3-none-any.whl (6.4 kB) Copy SHA256 Checksum SHA256 py3 Wheel Aug 16, 2017
django-db-constraints-0.3.0.tar.gz (4.3 kB) Copy SHA256 Checksum SHA256 Source Aug 16, 2017

Supported By

WebFaction WebFaction Technical Writing Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Rackspace Rackspace Cloud Servers DreamHost DreamHost Log Hosting