Note: This is basically a standalone version of the JSONB support in the Postgres contrib package of the Django master branch, targeted for the Django 1.9 release.
1.9
A field for storing JSON encoded data. In Python the data is represented in its Python native format: dictionaries, lists, strings, numbers, booleans and None.
Note
PostgreSQL has two native JSON based data types: json and jsonb. The main difference between them is how they are stored and how they can be queried. PostgreSQL's json field is stored as the original string representation of the JSON and must be decoded on the fly when queried based on keys. The jsonb field is stored based on the actual structure of the JSON which allows indexing. The trade-off is a small additional cost on writing to the jsonb field. JSONField uses jsonb.
As a result, the usage of this field is only supported on PostgreSQL versions at least 9.4.
We will use the following example model:
from django.contrib.postgres.fields import JSONField
from django.db import models
class Dog(models.Model):
name = models.CharField(max_length=200)
data = JSONField()
def __str__(self): # __unicode__ on Python 2
return self.namejsonfield.key
To query based on a given dictionary key, simply use that key as the lookup name:
>>> Dog.objects.create(name='Rufus', data={
... 'breed': 'labrador',
... 'owner': {
... 'name': 'Bob',
... 'other_pets': [{
... 'name': 'Fishy',
... }],
... },
... })
>>> Dog.objects.create(name='Meg', data={'breed': 'collie'})
>>> Dog.objects.filter(data__breed='collie')
[<Dog: Meg>]Multiple keys can be chained together to form a path lookup:
>>> Dog.objects.filter(data__owner__name='Bob')
[<Dog: Rufus>]If the key is an integer, it will be interpreted as an index lookup in an array:
>>> Dog.objects.filter(data__owner__other_pets__0__name='Fishy')
[<Dog: Rufus>]If the key you wish to query by clashes with the name of another lookup, use the jsonfield.contains lookup instead.
If only one key or index is used, the SQL operator -> is used. If multiple operators are used then the #> operator is used.
Warning
Since any string could be a key in a json object, any lookup other than those listed below will be interpreted as a key lookup. No errors are raised. Be extra careful for typing mistakes, and always check your queries work as you intend.
jsonfield.contains
jsonfield.contained_by
jsonfield.has_key
jsonfield.has_any_keys
jsonfield.has_keys
~django.contrib.postgres.fields.JSONField shares lookups relating to containment and keys with ~django.contrib.postgres.fields.HStoreField.
contains <hstorefield.contains>(accepts any JSON rather than just a dictionary of strings)contained_by <hstorefield.contained_by>(accepts any JSON rather than just a dictionary of strings)has_key <hstorefield.has_key>has_any_keys <hstorefield.has_any_keys>has_keys <hstorefield.has_keys>