PostgreSQL native array fields extension for Django.
PostgreSQL array field for Django.
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.
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()
This is a sample example of creating objects with array fields.
>>> Register.objects.create(points = [1,2,3,4]) <Register: Register object> >>> Register2.objects.create(texts = [['Hello', 'World'], ['Hola', 'Mundo']]) <Register2: Register2 object>
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.
- Querysets using expressions package can not be used as subqueries. Because alias propagation is not working properly.