Fetching nested child records in django framework

Question

This project is being developed in python and django.

As per my requirement I want to querying all the products from the categories upto two to three level up...

My entity structure is as follows.

Category:
- Name
- ParentCategory

Product:
- ID
- Name
- Category

Here are sample records which I want to query.

Category:
 - Name: Apparel | Parent:None
 - Name: Shirt | Parent: Apparel
 - Name: TShirts | Parent: Apparel
 - Name: MaleTShirts | Parent:TShirts
 - Name: FemaleTShirts | Parent: TShirts
 - Name:Electornics | Parent:None

Product:
 - ID:1 | Name:ABC | Category:MaleTShirt
 - ID:2 | Name:XYZ | Category:FemaleTShirt
 - ID:3 | Name:JKL | Category:Shirt

Problem is, user should access these products from any level in category. For example,

When user selects category Apparel, product ABC, XYZ, and JKL should appear in the resultset.
When user selects category TShirts, product ABC and XYZ should appear in the resultset.
When user selects category MaleTShirts, only ABC should appear in the resultset.
When user selects category FemaleTShirts, only XYZ should appear in the resultset.

Any idea how the model classes should be structured, and how should we query so that desired results can be achieved.

Any suggestions would be helpful. It would be good if code is also provided.

allait · Accepted Answer · 2010-11-01 15:22:19Z

1

You can use something like django-mptt to store hierarchical data(your Categories model) in a database. It provides additional methods to retrieve all descendants of certain element. And using Product.objects.filter(category__in=...) you can then retrieve all products, related to selected category's descendants.

answered Nov 1, 2010 at 15:22

allait

3,3693 gold badges26 silver badges9 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Pascal Qyy · Accepted Answer · 2010-11-01 15:14:15Z

1

What about thinking an implementation of 2-interval graphs ?

answered Nov 1, 2010 at 15:14

Pascal Qyy

4,5124 gold badges34 silver badges46 bronze badges

Comments

mouad · Accepted Answer · 2010-11-01 15:54:53Z

1

i think your model look just fine with the fields that you have there; and for the query you can do (it's not tested):

list_categories = []

head_category = Category.objects.filter(parent_category=request.GET['category'])

while head_category:
     # Transform the Queryset to a list.
     head_category = [category.category for category in head_category]

     # Put all the new categories in the list
     for category in head_category:
         list_categories.append(category)

     # Get child categories of the current categories.
     child_category = Category.objects.filter(parent_category__in=head_category)
     head_category = child_category

# Get all product from those category list.
Product.objects.filter(category__parent_category__in=list_categories)

edited Nov 1, 2010 at 15:54

answered Nov 1, 2010 at 15:28

mouad

70.5k18 gold badges117 silver badges106 bronze badges

Comments

thraxil · Accepted Answer · 2010-11-01 15:13:59Z

0

For hierarchical data, you probably want to start using django-treebeard.

answered Nov 1, 2010 at 15:13

thraxil

5,2412 gold badges21 silver badges10 bronze badges

Collectives™ on Stack Overflow

Fetching nested child records in django framework

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related