django-pgjsonb 0.0.4

Django Postgres JSONB Fields support with lookups

# django-pgjsonb
Django Postgres JSONB Fields support with lookups

Originaly inpired by [django-postgres](https://bitbucket.org/schinckel/django-postgres/)

Install
=======
pip install django-pgjsonb

Use
===
from django_pgjsonb import JSONField
class Article(models.Model):
meta=JSONField([null=True,default={}])

Lookups
=======
###Contains wide range of lookups support natively by postgres

1. `has` :if field has specific key *`("?")`*

Artile.objects.filter(meta__has="author")
2. `has_any` : if field has any of the specific keys *`("?|")`*

Artile.objects.filter(meta__has_any=["author","date])
3. `has_all` : if field has all of the specific keys *`("?&")`*

Artile.objects.filter(meta__has_all=["author","date])
4. `contains` : if field contains the specific keys and values *`("@>")`*

Article.objects.filter(meta__contains={"author":"yjmade","date":"2014-12-13"})
5. `in` or `contained_by` : if all field key and value contain by input *`("<@")`*

Artile.objects.filter(meta__in={"author":"yjmade","date":"2014-12-13"})
6. `len` : the length of the array ,transform to int,and can followed int lookup like gt or lt *`("jsonb_array_length()")`*

Artile.objects.filter(meta__authors__len__gte=3)
Article.objects.filter(meta__authors__len=10)
7. `as_(text,int,float,bool,date,datetime)` : transform json field into sepcific data type so that you can follow operation of this type *`("CAST(FIELD as TYPE)")`*

Article.objects.filter(meta__date__as_datetime__year__range=(2012,2015))
Article.objects.filter(meta__view_count__as_float__gt=100)
Article.objects.filter(meta__title__as_text__iregex=r"^\d{4}")
8. `path_(PATH)` : get the specific path, path split by '_' *`("#>")`*

Article.objects.filter(meta__path_author_articles__contains="show me the money")

Add function to QuerySet
========================
1.`select_json(field_name="JSON_PATHS")`

JSON_PATHS in format of path seperate by "__",like "meta__location__geo_info".it will use queryset extra method to transform a value inside json as a field.

Article.objects.select_json(geo="meta__location__geo_info")`
This operation will translate to sql as

SELECT "meta"->'location'->>'geo_info' as "geo"
After select_json ,then the field_name can be operate in values() and values_list() method,so that

1. select only one sepecific value inside json
2. to group by one value inside json

is possible.

Demo:

1.Article.objects.all().select_json(tags="meta__tags").values_list("tags")
#select only "meta"->'tags'
2.Article.objects.all().select_json(author_name="meta__author__name")
.values("author_name").annotate(count=models.Count("author_name"))
#GROUP BY "meta"->'author'->'name'




#####For more infomation about raw jsonb operation,please see [PostgreSQL Document](http://www.postgresql.org/docs/9.4/static/functions-json.html)