Use a collection on mongoid that does not have a model - mongodb

Question

I need to run a collection on Mongoid but this collection does not have a model, so i cant use it like: Project.collection.map_reduce( ..., :query => scoped.selector)
Does anyone know how could i do this?
Thanks

Answer 1

Here's an answer/example that works for Mongoid 3.1.5 / Moped 1.5.1, hope that it helps.
Please respond with your version info if you want something more specific to your environment.
Note that since you don't have a Mongoid model,
you loose the facilities of ODM level and have to drop down to the Moped driver level.
test/unit/session_test.rb
require 'test_helper'
require 'pp'
class SessionTest < ActiveSupport::TestCase
def setup
#session = Mongoid.default_session
#collection_name = 'project'
#collection = #session[#collection_name]
#collection.drop
end
test "collection map-reduce without model" do
puts "\nMongoid::VERSION:#{Mongoid::VERSION}\nMoped::VERSION:#{Moped::VERSION}"
docs = [
{'name' => 'Charlie', 'gender' => 'M', 'age' => 11},
{'name' => 'Lucy', 'gender' => 'F', 'age' => 13},
{'name' => 'Sally', 'gender' => 'F', 'age' => 15},
{'name' => 'Linus', 'gender' => 'M', 'age' => 11},
{'name' => 'Snoopy'},
]
#collection.insert(docs)
assert_equal docs.size, #collection.find.to_a.size
pp #session.command(
:mapReduce => #collection_name,
:map => 'function(){ emit(this.gender, this.age); }',
:reduce => 'function(key, values){ return Array.sum(values)/values.length; }',
:out => { :inline => 1 },
:query => { 'age' => { '$exists' => true } }
)['results']
end
end
$ rake test
Run options:
# Running tests:
[1/1] SessionTest#test_collection_map-reduce_without_model
Mongoid::VERSION:3.1.5
Moped::VERSION:1.5.1
[{"_id"=>"F", "value"=>14.0}, {"_id"=>"M", "value"=>11.0}]
Finished tests in 0.111151s, 8.9968 tests/s, 8.9968 assertions/s.
1 tests, 1 assertions, 0 failures, 0 errors, 0 skips