Mongoid query by reference attribute

Question

here is a simple structure:

class Dinner
  belongs_to :user
  field :name

class User
  has_many :dinners
  field :name

now, what i want is to find all the dinners hosted by 'John'. looking for something like:

Dinner.where('user.name' => 'john')

the problem is that i cannot find any way to query by referenced attribute. any suggestions?

Dinner.includes(:user).where(:name => 'john') Is this not working? — Sachin R
– Sachin R, Commented Jan 31, 2013 at 4:34
@SachinR, no because Dinner also can have the name attrubute — Sagiv Ofek
– Sagiv Ofek, Commented Jan 31, 2013 at 5:11
@SachinR you confuse it with active record stuff. you can't do it on mongoid. — Sagiv Ofek
– Sagiv Ofek, Commented Jan 31, 2013 at 5:32
Can you provide all the conditions you require for the query? — Jason Prins
– Jason Prins, Commented Feb 1, 2013 at 10:00

cthulhu · Accepted Answer · 2013-01-31 15:36:16Z

3

I think it just won't work with your model. AFAIK querying by nested attributes works only for embedded documents. You have two options:

Dinner.where(user: User.find_by(name: 'john'))

Or store user name directly in Dinner. It's redundant, but makes your query simplier.

MongoDB is not relational database and doesn't support joins.

answered Jan 31, 2013 at 14:39

cthulhu

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