This error is raised when trying to eager load a polymorphic association using a JOIN. Eager loading polymorphic associations is only possible with ActiveRecord::Relation#preload.

Methods

Class Public methods

new(reflection = nil)

📝 Source code 
# File activerecord/lib/active_record/associations.rb, line 244
    def initialize(reflection = nil)
      if reflection
        super("Cannot eagerly load the polymorphic association #{reflection.name.inspect}")
      else
        super("Eager load polymorphic error.")
      end
    end
🔎 See on GitHub