Mongoid Search by Array of Association Id's

Question

I have a Rails 4.2, Mongoid 4 project with these models:

class Customer #aka Company
  include Mongoid::Document

  has_many :branches
end

class Branch
  include Mongoid::Document  

  field :name, type: String, default: ""

  belongs_to :customer
end

I want to find all the Customers (aka Companies) that have a branch with name "New York". I would think that this code would work:

branches = Branch.where(name: "New York").map(&:_id)
=> [BSON::ObjectId('54f76cef6272790316390100')]
Customer.where(:branch_ids => branches).entries

However, it always returns an empty array, no matter what I try. In place of branch_ids, I've also tried branches, branch, branches_id, and others, but to no avail. I've also tried to convert the BSON::ObjectID to plain string, but that doesn't work either.

So, basically, how can I search a model based on an array of association ids? Thanks.

What does it return : `Customer.elem_match(branches: { name: "New York" })` — Sharvy Ahmed, Mar 11 '15 at 17:16
And this - `Customer.where(:branches.elem_match => { name: "New York" })` — Sharvy Ahmed, Mar 11 '15 at 17:20
@SharvyAhmed Both return an empty array (after calling `.entries`) — Ryan K, Mar 11 '15 at 17:23
could you try without .entries, try .to_a at the end and let us know the output — Sharvy Ahmed, Mar 11 '15 at 17:30
With `.to_a`, it still returns empty array. Without `.entries` or `.to_a` it returns a valid `Mongoid::Criteria`, but that in itself isn't helpful to me. — Ryan K, Mar 11 '15 at 17:33
Did you try this to get the branches ids `branches = Branch.where(name: "New York").map { |b| b.id.to_s }` ? Then `Customer.where(branch_id: branches).entries` ? `branch_id` would be the field name, instead of branch_ids. — Sharvy Ahmed, Mar 11 '15 at 17:37
Yeah, it's the same thing with or without the `BSON::ObjectID`. — Ryan K, Mar 11 '15 at 17:39
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/72784/discussion-between-sharvy-ahmed-and-ryan-k). — Sharvy Ahmed, Mar 11 '15 at 17:42

Santhosh · Accepted Answer · 2015-03-11T16:23:01.327

1

If the relations are

Customer has_many :branches and

Branch belongs_to :customer,

Then branches collection will have a customer_id column and not the reverse. So you can do

cust_ids = Branch.where(name: "New York").map(&:customer_id)
Customer.find(cust_ids)

Since you need only the customer ids from the first query, it is advisable to use pluck

cust_ids = Branch.where(name: "New York").pluck(:customer_id)

edited Mar 11 '15 at 16:23

answered Mar 11 '15 at 16:17

Santhosh

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That does work (don't know why I didn't think of it), but it seems like a workaround. I know that there isn't a column of `branch_ids`, but there is a method. I just don't know if you can search via a method. – Ryan K Mar 11 '15 at 16:43

score 0 · Answer 2 · answered Mar 11 '15 at 17:27

You can use Symbol#elem_match like this:

Customer.where(:branches.elem_match => { name: "New York" })

And Queryable#elem_match like this:

Customer.elem_match(branches: { name: "New York" })

Both query will give return you Customers of 'New York' branches.

Mongoid Search by Array of Association Id's

2 Answers2