Mongoid matches? does not support $elemMatch

class Subdoc

  include Mongoid::Document

  embedded_in :foo

  field :a

  field :b

end

class Foo

  include Mongoid::Document

  embeds_many :subdocs

end

f = Foo.new

f.subdocs.new(:a => 1, :b => 1)

f.subdocs.where(:a => 1).first

=> #<Subdoc _id: 57912b932774e24d68ce123f, a: 1, b: 1>

f.subdocs.where(:$elemMatch => {:a => 1}).first

=> nil