Does the update_all method in ActiveRecord return the number of rows?

I want to set the 'lock' column on a row only if it is not already set. Race conditions are likely and performance is important so this must be done in a single query. I think the solution should look like this:

开发者_开发问答class MyModel
  def lock(worker)
    cnt = MyModel.where(id: self.id, lock: nil).update_all(:lock=>worker.name)
    cnt == 1
  end
end

Does the update_all method actually return the number of rows effected like it does in DataMapper?

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Yes, it does in ActiveRecord as in DataMapper