How to organise a many to many relationship in MongoDB

Posted by Gareth Elms on Stack Overflow See other posts from Stack Overflow or by Gareth Elms
Published on 2011-01-29T22:35:08Z Indexed on 2011/01/29 23:26 UTC
Read the original article Hit count: 186

Filed under:

mongodb

|

many-to-many

|

relational-database

|

document-database

I have two tables/collections; Users and Groups. A user can be a member of any number of groups and a user can also be an owner of any number of groups. In a relational database I'd probably have a third table called UserGroups with a UserID column, a GroupID column and an IsOwner column.

I'm using MongoDB and I'm sure there is a different approach for this kind of relationship in a document database. Should I embed the list of groups and groups-as-owner inside the Users table as two arrays of ObjectIDs? Should I also store the list of members and owners in the Groups table as two arrays, effectively mirroring the relationship causing a duplication of relationship information?

Or is a bridging UserGroups table a legitimate concept in document databases for many to many relationships?

Thanks

© Stack Overflow or respective owner

Related posts about mongodb

MongoDB usage best practices

as seen on ASP.net Weblogs - Search for 'ASP.net Weblogs'
The project I'm working on uses MongoDB for some stuff so I'm creating some documents to help developers speedup the learning curve and also avoid mistakes and help them write clean & reliable code. This is my first version of it, so I'm pretty sure I will be adding more stuff to it, so stay tuned… >>> More
Errors trying to run MongoDB

as seen on Ask Ubuntu - Search for 'Ask Ubuntu'
I'm running Ubuntu Server 12.04 (32 bit) on an old (1998) computer. Everything's working fine until I try and start MongoDB. somekittens@DLserver01:~$ mongo MongoDB shell version: 2.2.2 connecting to: test Sun Dec 16 22:47:50 Error: couldn't connect to server 127.0.0.1:27017 src/mongo/shell/mongo… >>> More
push new value to mongodb inner array - mongodb/php

as seen on Stack Overflow - Search for 'Stack Overflow'
hi i have this document in mongo: { "_id": ObjectId("4d0b9c7a8b012fe287547157"), "done_by": ["1"] } and i want to add another value to "done_by" field, so my expected document will be:: { "_id": ObjectId("4d0b9c7a8b012fe287547157"), "done_by": ["1","2","3"] } i try this: $conn… >>> More
Write-only collections in MongoDB

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm currently using MongoDB to record application logs, and while I'm quite happy with both the performance and with being able to dump arbitrary structured data into log records, I'm troubled by the mutability of log records once stored. In a traditional database, I would structure the grants for… >>> More
How to install mongoDB on windows?

as seen on Stack Overflow - Search for 'Stack Overflow'
Hi! I am trying to test out mongoDB and see if it is anything for me. I downloaded the 32bit windows version, but have no idea on how to continue from now on. I normally use the WAMP services for developing on my local computer. Can i run mongoDB on Wamp? However, what's the best (easiest!) way… >>> More

Related posts about many-to-many

Self referencing symmetrical Hibernate Map Table using @ManyToMany

as seen on Stack Overflow - Search for 'Stack Overflow'
I have the following class public class ElementBean { private String link; private Set<ElementBean> connections; } I need to create a map table where elements are mapped to each other in a many-to-many symmetrical relationship. @ManyToMany(targetEntity=ElementBean.class) @JoinTable( … >>> More
Django ManyToMany join query

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm sure this is really simple, but I can't for the life of me find any documentation explaining how to do this. How do I get the results of a ManyToMany field inside a join as opposed to doing this: {% for tag in article.tags.all %} Which results in an extra query? What I'd like to do is fetch… >>> More
django ManyToMany through help

as seen on Stack Overflow - Search for 'Stack Overflow'
Hay I've got a question about relationships. I want to Users to have Friendships. So a User can be a friend with another User. I'm assuming i'll need to use the ManyToManyField, through a Friendship table. But i cannot get it to work. Any ideas? Here are my models. class User(models.Model): … >>> More
Limiting choices from an intermediary ManyToMany junction table in Django

as seen on Stack Overflow - Search for 'Stack Overflow'
Background I've created three Django models—Inventory, SalesOrder, and Invoice—to model items in inventory, sales orders for those items, and invoices for a particular sales order. Each sales order can have multiple items, so I've used an intermediary junction table—SalesOrderItems—using the through… >>> More
What's best practice to check if an object is part of a ManyToMany relationship in Django

as seen on Stack Overflow - Search for 'Stack Overflow'
from an instance of Site with a ManyToMany relationship to Kiosk, i'd like to check if a Kiosk object is part of the relationship. I could do self.apps.get(id=app_id).exists() and check if True or self.apps.get(id=app_id) and catch the ObjectDoesNotExist error or self.apps.filter(id=app_id)… >>> More