Using `only` can cause an association reset

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    • Type: Task
    • Resolution: Done
    • 3.0.2
    • Affects Version/s: None
    • Component/s: None
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      Consider the following models

      class User
  include Mongoid::Document

  has_and_belongs_to_many :tags, inverse_of: nil
  field :email
  field :social_profile
  # ... other user fields
end

class Tag
  include Mongoid::Document
  # ... tag fields, nothing fancy here
end

      The following code updates the social_profile field using only to limit the amount of data loaded 

      User.where(social_profile: nil).only(:email).each do |user|
  user.social_profile = lookup_service.load_profile(user.email)
  user.save!
end

      This loop results in tags being reset on all matching users except for the first one. FWIW it used to keep tags for all users in Mongoid 2.x

              Assignee:
              Unassigned
              Reporter:
              Alex Tsibulya
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                Created:
                Updated:
                Resolved: