class ActiveRecord::PredicateBuilder

def self.expand(klass, table, column, value)
  queries = []
  # Find the foreign key when using queries such as:
  # Post.where(author: author)
  #
  # For polymorphic relationships, find the foreign key and type:
  # PriceEstimate.where(estimate_of: treasure)
  if klass && value.class < Base && reflection = klass.reflect_on_association(column.to_sym)
    if reflection.polymorphic?
      queries << build(table[reflection.foreign_type], value.class.base_class)
    end
    column = reflection.foreign_key
  end
  queries << build(table[column], value)
  queries
end