CODEWITHSUNDEEP
pythondjangodjango-modelsdjango-rest-framework
Karesh A
Karesh A

Reputation: 1751

Django REST serialize output - group by foreign keys

I have models like below.

Restaurant Model

class Restaurant(models.Model):

    name = models.CharField(max_length=40, verbose_name='Name')

Menu Model

class Menu(models.Model):

    name = models.CharField(max_length=40, unique=True, verbose_name='menu name')

Item Model

class Item(models.Model):

    restaurant = models.ForeignKey(Restaurant)
    menu = models.ForeignKey(Menu)

    name = models.CharField(max_length=500)
    price = models.IntegerField(default=0)

I want to get the menus for the shop id.

How can I group my results by menu for the restaurant id ?

call GET /menus/restaurant_id

Sample.

{
 name: menu name 1
 items: [ {item1}, {item2}]
},
{
 name: menu name 2
 items: [ {item1}, {item2}]
}

Thanks..

Upvotes: 0

Views: 418

Answers (1)

devxplorer
devxplorer

Reputation: 637

The only thing i can find it's postgres specific aggregation function ArrayAgg

You can use it like this:

from django.contrib.postgres.aggregates import ArrayAgg

Item.objects.filter(restaurant_id=1).values('menu__name').annotate(items=ArrayAgg('name'))

# example output: 
# [
#     {
#         'menu__name': 'menu1',
#         'items': ['item1', 'item2']
#     },
#     {
#         'menu__name': 'menu2',
#         'items': ['item3', 'item4']
#     },
# ]

Such qs performs next raw sql query:

SELECT
  "appname_menu"."name",
  ARRAY_AGG("appname_item"."name") AS "items"
FROM "appname_item"
  INNER JOIN "appname_menu" ON ("appname_item"."menu_id" = "appname_menu"."id")
WHERE "appname_item"."restaurant_id" = 1
GROUP BY "appname_menu"."name"

Probably it can help you.

Upvotes: 1

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