array_ids.rb

class Templates < ROM::Relation[:sql]
  schema do
    attribute :possible_resolution_ids, Types::PG::Array('bigint')
    
    associations do
      has_many :resolutions,
               as: :possible_resolutions,
               relation: :resolutions,
               view: :for_possible_resolutions_in_templates,
               foreign_key: :template_id,
               override: true
    end
  end
end

class Resolutions < ROM::Relation[:sql]
  def for_possible_resolutions_in_templates(_assoc, templates)
    template_id = templates.pluck(:template_id)[0]

    select_append { int::cast(`'#{ template_id }'`, 'bigint').as(:template_id) }.
      where(resolution_id: templates.pluck(:possible_resolution_ids).flatten(1))
  end
end