django-postgres-extra 1.0

Bringing all of PostgreSQL's awesomeness to Django.

django-postgres-extra

django-postgres-extra aims to make all of PostgreSQL’s awesome features available through the Django ORM. We do this by taking care of all the hassle. As opposed to the many small packages that are available to try to bring a single feature to Django with minimal effort. django-postgres-extra goes the extra mile, with well tested implementations, seamless migrations and much more.

With seamless we mean that any features we add will work truly seamlessly. You should not have to manually modify your migrations to work with fields and objects provided by this package.

This package requires Python 3.5 or newer and Django 1.10 or newer.

Focus

Currently, we are working on bringing the following features to Django:

• https://www.postgresql.org/docs/9.1/static/hstore.html

  • UNIQUE constraints

  • All operators

  • GiST and GIN indexes

• https://www.postgresql.org/docs/9.1/static/ltree.html

  • All operators

  • All functions

  • Unique indexes

  • GiST and GIN indexes

• https://www.postgresql.org/docs/9.5/static/sql-insert.html#SQL-ON-CONFLICT

  • ON CONFLICT UPDATE

  • ON CONFLICT DO NOTHING

The current TODO list looks like this:

• Add support for ON CONFLICT X.

• Add support for ltree.

Installation

1. Install the package from PyPi:

   $ pip install django-postgres-extra

2. Add postgres_extra and django.contrib.postgres to your INSTALLED_APPS:

   INSTALLED_APPS = [
       ....
   
       'django.contrib.postgres',
       'psqlextra'
   ]

3. Set the database engine to psqlextra.backend:

   DATABASES = {
       'default': {
           ...
           'ENGINE': 'psqlextra.backend'
       }
   }

Usage

• psqlextra.models.PostgresModel

  Inheriting your models from this gives you access to the PostgresManager, which exposes:

  • upsert:

    • Native, single query, concurrency safe upsert:

      from psqlextra.models import PostgresModel
      
      class MyModel(PostgresModel):
          title = models.CharField(unique=True)
      
      pk1 = MyModel.objects.upsert(title='beer')
      pk2 = MyModel.objects.upsert(title='beer')
      
      assert pk1 == pk2

  • upsert_and_get:

    • Native, single query, concurrency safe upsert + select:

      from psqlextra.models import PostgresModel
      
      class MyModel(PostgresModel):
          title = models.CharField(unique=True)
      
      pk1 = MyModel.objects.upsert(title='beer')
      obj2 = MyModel.objects.upsert_and_get(title='beer')
      
      assert pk1 == obj2.pk

  Upserts use PostgreSQL’s ON CONFLICT clause. This instruct PostgreSQL to overwrite an existing row when it encounters a conflict (duplicate key). This happens in a single query. PostgreSQL guarentees concurrency safety for ON CONFLICT.

• psqlextra.fields.HStoreField

  Inherits from Django’s HStoreField but adds support for constraints:

  • uniqueness:

    • Enforce uniqueness for one or more key:

      from psqlextra.fields import HStoreField
      
      class MyModel(models.Model):
          title = HStoreField(uniqueness=['en', 'ro'])

    • Enforce uniqueness for one ore more keys together (similar to Django’s unique_together):

      from psqlextra.fields import HStoreField
      
      class MyModel(models.Model):
          title = HStoreField(uniqueness=[('en', 'ro')])

  • required:

    • Require one or more keys to be set:

      from psqlextra.fields import HStoreField
      
      class MyModel(models.Model):
          title = HStoreField(required=['h1', 'h2'])

FAQ - Frequently asked questions

1. Why do I need to change the database back-end/engine?

   We utilize PostgreSQL’s hstore data type, which allows you to store key-value pairs in a column. In order to create UNIQUE constraints on specific key, we need to create a special type of index. We could do this without a custom database back-end, but it would require everyone to manually write their migrations. By using a custom database back-end, we added support for this. When changing the uniqueness constraint on a HStoreField, our custom database back-end takes care of creating, updating and deleting these constraints/indexes in the database.

2. I am already using a custom database back-end, can I still use yours?

   Yes. You can set the POSTGRES_EXTRA_DB_BACKEND_BASE setting to your current back-end. This will instruct our custom database back-end to inherit from the database back-end you specified. Warning: this will only work if the base you specified indirectly inherits from the standard PostgreSQL database back-end.

3. Does this package work with Python 2?

   No. Only Python 3.5 or newer is supported. We’re using type hints. These do not work well under older versions of Python.

4. Does this package work with Django 1.X?

   No. Only Django 1.10 or newer is supported.