djorm-ext-pgarray

PostgreSQL array field for Django.

• Blog post:

Introduction

Django by default, has a large collection of possible types that can be used to define the model. But sometimes we need to use some more complex types offered by PostgreSQL. In this case, we will look the integrating of PostgreSQL array with Django.

Quickstart

djorm-ext-pgarray exposes a simple django model field djorm_pgarray.fields.ArrayField. This accepts two additional parameters: dbtype that represents a postgresql type, and dimension that represents a dimension of array field.

This is a sample definition of model using a ArrayField:

from django.db import models
from djorm_pgarray.fields import ArrayField
from djorm_expressions.models import ExpressionManager

class Register(models.Model):
    name = models.CharField(max_length=200)
    points = ArrayField(dbtype="int")
    objects = ExpressionManager()

class Register2(models.Model):
    name = models.CharField(max_length=200)
    texts = ArrayField(dbtype="text", dimension=2) # this creates `points text[][]` postgresql field.
    objects = ExpressionManager()

Creating objects

This is a sample example of creating objects with array fields.

>>> Register.objects.create(points = [1,2,3,4])

>>> Register2.objects.create(texts = [['Hello', 'World'], ['Hola', 'Mundo']])

Using custom PostgreSQL data types

Some times we need use some other data types that postgresql offers for make arrays and djorm-ext-pgarray does not offers builtin support for it. Now, djorm-ext-pgarray supports a simple way to extend it:

class Register(models.Model):
    name = models.CharField(max_length=200)
    macs = ArrayField(dbtype="macaddr", type_cast=lambda x: str(x))
    # Same as previous line but uses str as callback directly
    # macs = ArrayField(dbtype="macaddr", type_cast=str)
    objects = ExpressionManager()

If type_cast patameter is not None, ArrayField ignores the no existence of a builtin cast function for some type and use a function passed throught type_cast argument.

How install it?

You can clone the repo from github and install with simple python setup.py install command. Or use a pip, for install it from Python Package Index.

pip install djorm-ext-pgarray

Additionally, you can install djorm-ext-expressions, that can help with complex queries using array fields.

Known issues

• Querysets using expressions package can not be used as subqueries. Because alias propagation is not working properly.