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Let me start with my use case. I have two different instance of mongoid database hosted per region based with similar model. And depending on user input, the code gets the results from respective mongo instance in my rails app. I am not sure what is the best way of doing this however I used Model.with approach and configured two clients in mongoid.yml.

With mongoid <5.0, this worked perfect. However, recently I am upgrading to mongoid 6.2 with which Model.with now accepts block and my query is not producing any results.

Heres example code.

I changed my code from below (mongoid <5 which worked fine)

results = SomeModel.with(client: "region1").where(name: 'John')

to (mongoid >= 6.2)

results = SomeModel.with(client: "region1") do |mymodel|
    mymodel.where(name: 'John')
end

With new code the results are empty. Not sure if I am doing anything wrong. However, below code works fine if want just one record:

results = SomeModel.with(client: "region1") do |mymodel|
    mymodel.where(name: 'John').first
end

I would really appreciate if there is any other idea for my use case.

R. V.
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1 Answers1

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I have only used Mongoid 6, and just recently, but maybe this will help. Though, it has nothing to do with the multiple clients case.

Well, #first is actually saying, from that criteria {name: 'john'} give me the first occurrence.

Isn't that when you call a #where, you are only declaring the criteria parameters, but the actual query isn't executed until you ask for the actual data?

I'm not 100% sure but.

:001 > Book.where(name: "my book")
 => #<Mongoid::Criteria
  selector: {"name"=>"my book"}
  options:  {}
  class:    Book
  embedded: false>

 :002 > Book.where(name: "my book").first
 => #<Book _id: 5954ae90ASDF10fe7739cbe, name: "my book", code: "ASDF-1234-qwer-3456">
 :003 >

Now, if you want the collection of data and not the criteria itself, you may want to call a method over that object, like #to_a, #to_json, #first, #last, iterate them with #each, or even use an operator like [0]. That will bring you the data that corresponds to the Criteria you declared earlier.

That's what i think, because when i throw a #where in a controller's method from my rails apps, and the result is rendered as JSON, a call to #as_json is implicit.

Maybe try to call a #to_a and get the full array of objects to return.

rccursach
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  • Thanks for the response. I understand simple use cases. The issue is in my first mongoid 6 'with' query above, results are in fact `Mongoid::Criteria` but its empty. Your suggestion of using `#to_a` works but it will hit the database which I only want when I am iterating through `Mongoid::Criteria`. – R. V. Jul 23 '17 at 17:19