has_many eager loading perfomance problem

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    • Type: Task
    • Resolution: Done
    • 4.0.0 final
    • Affects Version/s: None
    • Component/s: None
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      With new eager loading, when relation is eager loaded and empty, it triggers extra database query on each request to association. 

      class Post
  include Mongoid::Document

  belongs_to :person
end

class Person
  include Mongoid::Document

  has_many :posts
end

100.times do |i|
  Person.create!
end

# generates 102 requests to database
count_queries do
  Person.includes(:posts).each do |person|
    person.posts.to_a
  end
end

              Assignee:
              Arthur Nogueira Neves
              Reporter:
              xronos-i-am
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                Created:
                Updated:
                Resolved: