Can you query based on a referred document?

[AlvesJorge]

Going with the example schema:

class Band
include Mongoid::Document
has_many :awards
field :name, type: String
end
 
class Award
include Mongoid::Document
belongs_to :band
field :prize_money, type: String
field :name, type: String
end

I know that if Band embedded Award I could simply query

Band.where(award.prize_money: "10k") # [Band1, Band2]

But if Band only refers to award how could I perform a similar query?
This doesn't work:

Award.where(prize_money:  "10k", "band.name": "Depeche Mode")

Is there a method that would allow for band to be populated for query purposes?
Something like:

Award.with_association(:band).where(prize_money:  "10k", "band.name": "Depeche Mode")

Using aggregate returns BSON documents, which I don't love.
Embedding awards would stop me from querying for awards directly, which I don't want.
I created an abstraction for this purpose, but I don't love it either, since it requires the knowledge of it's existence.

    def self.query_with_band(award_query, band_query)
      awards = Award.where(unit_query)
      band_ids = awards.pluck(:band_id)
      bands = Band.in(id: band_ids).where(band_query)
      award_query.in(band_id: bands.pluck(:id))
    end

Which I then call like so

Award.query_with_band({prize_money: "10k"}, {name: "Depeche Mode"})

TL;DR: Is there a method to allow for querying for refered associations as if they are embedded? :)

PS: I realize that this question may be more geared towards the mongo ruby gem :)

[jamis]

Hello @AlvesJorge -- Mongoid does not currently support this style of query; you would need to split it into two queries currently (one to fetch the matching band ids, and the other to find the Award documents for those bands, as you've done in your workaround).

If you're using the driver directly, you can do this with an aggregation pipeline with a '$lookup' stage. We plan to add a aggregation pipeline builder DSL to Mongoid "soon", which could likely become a foundation for a feature like what you're describing.

[AlvesJorge]

aggregation pipeline builder DSL to Mongoid "soon", which could likely become a foundation for a feature like what you're describing

I can imagine that being the case :)
Thank you for the reply jamis