Django Postgres composite types

An implementation of Postgres' composite types for Django.

Usage

Install with:

pip install django-postgres-composite-types

Define a type and add it to a model:

from django.db import models
from postgres_composite_type import CompositeType

class Address(CompositeType):
    """An address."""

    address_1 = models.CharField(max_length=255)
    address_2 = models.CharField(max_length=255)

    suburb = models.CharField(max_length=50)
    state = models.CharField(max_length=50)

    postcode = models.CharField(max_length=10)
    country = models.CharField(max_length=50)

    class Meta:
        db_type = 'x_address'  # Required


class Person(models.Model):
    """A person."""

    address = Address.Field()

An operation needs to be prepended to your migration:

import address
from django.db import migrations


class Migration(migrations.Migration):

    operations = [
        # Registers the type
        address.Address.Operation(),
        migrations.AddField(
            model_name='person',
            name='address',
            field=address.Address.Field(blank=True, null=True),
        ),
    ]

Examples

Array fields:

class Card(CompositeType):
    """A playing card."""

    suit = models.CharField(max_length=1)
    rank = models.CharField(max_length=2)

    class Meta:
        db_type = 'card'


class Hand(models.Model):
    """A hand of cards."""
    cards = ArrayField(base_field=Card.Field())

Nested types:

class Point(CompositeType):
    """A point on the cartesian plane."""

    # pylint:disable=invalid-name
    x = models.IntegerField()
    y = models.IntegerField()

    class Meta:
        db_type = 'x_point'  # Postgres already has a point type


class Box(CompositeType):
    """An axis-aligned box on the cartesian plane."""
    class Meta:
        db_type = 'x_box'  # Postgres already has a box type

    top_left = Point.Field()
    bottom_right = Point.Field()

Gotchas and Caveats

The migration operation currently loads the current state of the type, not the state when the migration was written. A generic CreateType operation which takes the fields of the type would be possible, but it would still require manual handling still as Django's makemigrations is not currently extensible.

Changes to types are possible using RawSQL, for example:

operations = [
    migrations.RunSQL([
        "ALTER TYPE x_address DROP ATTRIBUTE country",
        "ALTER TYPE x_address ADD ATTRIBUTE country integer",
    ], [
        "ALTER TYPE x_address DROP ATTRIBUTE country",
        "ALTER TYPE x_address ADD ATTRIBUTE country varchar(50)",
    ]),
]

However, be aware that if your earlier operations were run using current DB code, you will already have the right types (bug #8).

It is recommended to that you namespace your custom types to avoid conflict with future PostgreSQL types.

Lookups and indexes are not implemented yet (bug #9, bug #10).

Authors

• Danielle Madeley danielle@madeley.id.au
• Tim Heap hello@timheap.me

License

(c) 2016, Danielle Madeley danielle@madeley.id.au

All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

3. Neither the name of the copyright holder nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

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