Nosql many-to-many

Question

What is the accepted pattern for handling many-to-many relationships in a document database design?

Answer 1

How you want to model the many-to-many will depend on what kind of queries you want to ask, how you want to update the data, etc... Say we have foos related to bars in a many to many fashion.

You could model a foo as

{
   'bars': ['bar1', 'bar2', 'bar3']
}

and model a bar as

{
   'foos': ['foo_x', 'foo_y', 'foo_z']
}

Or you could model the graph or relations between foo and bar as individual documents themselves

{
    from: 'foo1',
    to: 'bar1'
}

{
   from: 'foo1',
   to: 'bar2'
}

{  
   from: 'foo2',
   to: 'bar3
}

{
  from 'foo3',
  to: 'bar3'
}

There are plenty of other ways too. How you want to do it will depend on the questions you want to ask, the operations you want to support, what you want to be efficient, and the indexing available in the database.